Mutant tumor necrosis factor receptor (tnfr) ligands and methods of making and using same

ABSTRACT

Methods for constructing efficient inhibitors of target TNF superfamily receptors, single chain target TNF superfamily ligands that inhibit of target TNF superfamily receptors while failing to engage or inhibit non-target TNF superfamily receptors, and methods of their use to treat diseases are provided. Single chain RANKL, TNF, and TRAIL ligands that effectively inhibit their target receptors while failing to inhibit non-target TNF superfamily receptors are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of Ser. No. 15/894,502 filed 12 Feb. 2018, which is a continuation of Ser. No. 14/796,827, now patent U.S. Pat. No. 9,914,761, filed 10 Jul. 2015, which claims the benefit of U.S. Provisional patent application Ser. No. 62/023,117, filed 10 Jul. 2014. Each of the above references is incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT

This invention was made with government support under AR032788 and AG039896 awarded by the National Institutes of Health. The government has certain rights in the invention.

REFERENCE TO SEQUENCE LISTING SUBMITTED ELECTRONICALLY

The content of the electronically submitted sequence listing in ASCII text file (Name53047.144425_SEQ LISTING_ST25.txt; Size: 102,715 bytes (MS-DOS); and Date of Creation: Jul. 10, 2015) filed with the application is incorporated herein by reference in its entirety.

BACKGROUND

Excess activation of TNF superfamily (TNFsf) receptors can induce a myriad of pathological conditions (1, 2). While some biological agents have positively impacted the course of these diseases, each carries substantial complications (3). The TNFsf member RANKL is a cytokine that regulates osteoclast formation and function (4-7) and excess activation of its receptor, RANK, can promote many if not most forms of pathological bone loss. RANKL exists as a homotrimer in solution (8). Each of the three interfaces separating the monomers contains a binding groove accepting a single copy of RANK or the anti-osteoclastogenic decoy receptor, osteoprotegerin (OPG) (9-11). As each trimer assembles, loops and strands at the edges of apposed monomers combine to form the sides of the receptor-binding clefts. It is the shape of the binding clefts which determine receptor selectivity. For wild-type RANKL, each of the three identical receptor-binding clefts, spaced equally around the outside of the cytokine, can accept a single copy of RANK or the anti-osteoclastogenic decoy receptor, osteoprotegerin (OPG)

RANKL, a member of the TNF superfamily, binds to multiple receptors (RANK and OPG) with different biological effects. Within this superfamily, there are several examples of cytokines demonstrating receptor promiscuity (17). For example, TNFα, which recognizes TNFR1 and TNFR2, is central to the pathogenesis of disabling disorders such as rheumatoid arthritis and psoriasis (18). Treatment of these diseases has been greatly facilitated by global TNFα blockade using humanized antibodies or soluble receptor (19, 20). As effective as these drugs are, they carry major complications such as predisposition to malignancy and serious infections, including tuberculosis (21, 22). Current evidence indicates that the positive effects of anti-TNFα therapy reflects suppressed activation of TNFR1, while negative consequences are due to inhibition of the pro-immune properties of TNFR2 (23, 24). For example, the osteolysis responsible for orthopedic implant loosening appears to be solely mediated by TNFR1 (Merkel et al., 1999; Am. Journ. Pathol. 154(1):203-210). In fact activation of TNFR1 promotes osteoclastogenesis, leading to bond resorption, while activation of TNFR2 inhibits it. Further, TNFR1 activation inhibits pre-osteoblast differentiation, and so blunts bone formation, while activation of TNFR2 does not (Abbas et al., 2003; Cytokine 22(1-2): 33-41. Thus TNFR2 signaling inhibits bone remodeling, but not bone formation, and so displays protective properties in the context of inflammatory osteolysis. Nago et al, 2011, J. Bone Miner. Metab; 29(6): 671-681. and Hussain et al., 2008, J. Bone Miner. Metab; 26(5):p469-477). The need for DR4 vs. DR5 specific TRAIL variants stems from the apparent DR4- or DR5-specific sensitivities of various tumors to selective receptor agonists. For example, acute myeloid leukemia appears to be more sensitive to a DR4-selective variant yet resistant to killing by a DR5-selective TRAIL variant (Szegezdi, Journal of Cellular and Molecular Medicine Volume 15, Issue 10, pages 2216-2231, October 2011). Additionally, it has been reported using several different chronic lymphocytic leukemia cell lines that an agonist antibody specific for DR4 induce apoptosis whereas an agonist antibody specific for DR5 fails to do so (Xiao, Leukemia and Lymphoma July 2011, Vol. 52, No. 7, Pages 1290-1301). Conversely, DR5-selective TRAIL variant was effective in killing a breast cancer cell line whereas a DR4-selective TRAIL variant was not despite similar expression of DR4 and DR5 in these cells (Kelley 2005 The Journal of Biological Chemistry, 280, 2205-2212). The sensitivity of various cancer types including primary cells and cell lines is reviewed extensively in van Roosmalen et al. (van Roosmalen Biochemical Pharmacology, Volume 91, Issue 4, 15 Oct. 2014, Pages 447-456). RANKL, TNF, and TRAIL interact with their receptors in a homologous fashion (9, 10, 25, 26).

“Novel variants of RANKL protein” WO2003059281 (PCT/US2003/000393) of Desjarlais, J. R., et al., and TNF Family Ligand Variants” US20140096274 A1 of Quax, W. J., et al. discuss RANKL variants. “Single-chain antagonist polypeptides” WO2001025277 of Andersen, K. V., et al. discusses modification of osteoprotegerin ligand. The articles “Crystal structure of the TRANCE/RANKL cytokine reveals determinants of receptor-ligand specificity” of Lam, J., Nelson, C. A., Ross, F. P., Teitelbaum, S. L., Fremont, D. H; J Clin Invest. 2001 October; 108(7):971-9 and “Structural and functional insights of RANKL-RANK interaction and signaling” of Liu, C., et al., J Immunol. 2010 Jun. 15; 184(12):6910-9 discuss structural features of RANKL.

The sole medically approved inhibitor of this pathway, denosumab, targets the cytokine itself but not its receptor and its effects last for 7-9 months (12). Given the profound suppression of bone remodeling accompanying cytokine removal or other anti-bone resorptive strategies, shorter acting agents are needed.

SUMMARY

The present inventors herein report a strategy for generating an effective inhibitor of RANK signaling and other members of the TNFsf. The inventors of the present teachings have developed RANKL variants that can inhibit RANK signaling. In various embodiments, a single chain RANK ligand of the present teachings can be an inhibitor of bone resorption. In various embodiments, a polypeptide of the present teachings can comprise or consist of three monomers of RANK ligand. In various embodiments, a RANK ligand trimer can comprise a combination of mutations which can recognize RANK ligand with high avidity but can fail to recognize osteoprotegrin. In some embodiments, a polypeptide of the present teachings can inhibit bone resorption in vivo, and can be used to treat or prevent bone loss diseases such as osteoporosis in a human or other mammalian subject. In some embodiments, a polypeptide of the present teachings can inhibit bone resorption in vitro.

In various embodiments, a single-chain RANKL, with a combination of blocked or high affinity RANK binding sites as disclosed herein, can arrest RANK signaling, and can thus function as an effective inhibitor of RANKL-mediated osteoclast formation and function.

In various embodiments, a RANKL polypeptide of the present teachings can combine high affinity and blocking mutations into a single-chain, and can serve as an effective inhibitor that can be receptor selective. In various configurations, this can provide a mechanism for blocking TNFR1 while sparing TNFR2, thereby reducing systemic complications. This strategy can be broadly applicable to all members of the pathologically relevant TNF superfamily.

Methods for constructing an inhibitor of a Tumor Necrosis Factor superfamily (TNFsf) member receptor comprising the step of combining in a single polypeptide chain: (i) at least one first mutated TNFsf monomer that comprises at least one first mutation that blocks binding of a TNFsf member comprising the first mutated monomer to its corresponding target Tumor Necrosis Factor superfamily receptor; and, (ii) at least one second mutated TNFsf monomer that comprises at least one second mutation that increases binding affinity of a TNFsf member comprising the second mutated monomer to the corresponding target Tumor Necrosis Factor superfamily receptor, wherein at least three mutated TNFsf monomers are combined in the single polypeptide chain are provided. Methods for constructing an inhibitor of a Tumor Necrosis Factor superfamily (TNFsf) member receptor comprising the step of combining in a single polypeptide chain: (i) at least one first mutated TNFsf monomer that comprises at least one first mutation that blocks binding of a TNFsf member comprising the first mutated monomer to its corresponding target Tumor Necrosis Factor superfamily receptor; and, (ii) at least one second mutated TNFsf monomer that comprises at least one second mutation that increases binding affinity of a TNFsf member comprising the second mutated monomer to the corresponding target Tumor Necrosis Factor superfamily receptor, wherein at least two mutated TNFsf monomers and a wild type TNFsf monomer are combined in the single polypeptide chain are also provided. In certain embodiments, the single polypeptide chain comprises: (i) two first mutated TNFsf monomers and one second mutated TNFsf monomer; or (ii) one first mutated TNFsf monomer and two second mutated TNFsf monomers. In certain embodiments of the aforementioned methods, (i) one, two, or three of the monomers comprise at least one third mutation that decreases binding affinity of a TNFsf member comprising the three monomers with the third mutation to a non-target Tumor Necrosis Factor superfamily receptor; (ii) the second mutation(s) is a bifunctional mutation that both increases binding affinity of a TNFsf member comprising or consisting of the second mutated monomer to the corresponding target Tumor Necrosis Factor superfamily receptor and decreases binding affinity of a TNFsf member comprising or consisting of the second mutated monomer to a non-target Tumor Necrosis Factor superfamily receptor; (iii) the first mutation is a bifunctional mutation that both blocks binding of a TNFsf member comprising or consisting of the first mutated monomer to its corresponding target Tumor Necrosis Factor superfamily receptor and decreases binding affinity of a TNFsf member comprising or consisting of the first mutated monomer to a non-target Tumor Necrosis Factor superfamily receptor; or (iv) the single chain polypeptide comprises any combination of (i), (ii), and (iii). In certain embodiments of the aforementioned methods, the first mutation is selected from the group consisting of an AA″-Loop mutation, a BC loop mutation, a mutation in the C-terminal half of strand C, a CD-Loop mutation, a mutation in the N-terminal half of strand D, a DE Loop mutation, a mutation in the E strand, an EF loop mutation, a mutation in the N-terminal half of strand D, a mutation in the DE loop, an FG loop mutation, a GH-loop mutation, a salt-bridge-disrupting mutation, and combinations thereof, and wherein the mutation comprises an insertion, a deletion, a substitution, or a combination thereof. In certain embodiments of the aforementioned methods, the TNFsf member is human Receptor Activator of Nuclear Factor κ B Ligand (RANKL), the target Tumor Necrosis Factor superfamily receptor is Receptor Activator of Nuclear Factor κ B (RANK), and the non-target Tumor Necrosis Factor superfamily receptor is Osteoprotegerin (OPG). In certain embodiments of the aforementioned method where the TNFsf is RANKL, the first mutation is selected from the group consisting of a substitution of AA″ loop residues 177-185, R223Q, R223A, R223Y, an insertion immediately C-terminal to R223, H225N, I249R, and combinations thereof; and wherein the second mutation or bifunctional mutation is selected from the group consisting of A172R, K195E, F270Y, H271Y, Q237H, Q237T, and combinations thereof. In certain embodiments of the aforementioned methods where the TNFsf member is human RANKL, the third mutation or the bifunctional mutation is selected from the group consisting of G192A, K195E, F270Y, H271Y, Q237H, Q237T, and combinations thereof. In certain embodiments of the aforementioned methods, the TNFsf member is human Tumor Necrosis Factor (TNF), the target Tumor Necrosis Factor superfamily receptor is Tumor Necrosis Factor Receptor 1 (TNFR1), and the non-target Tumor Necrosis Factor superfamily receptor is Tumor Necrosis Factor Receptor 2 (TNFR2). In certain embodiments of the aforementioned methods where the TNFsf member is human Tumor Necrosis Factor (TNF), the first mutation or bifunctional mutation is selected from the group consisting of N110Q, L151R, Y163Q, Y163G, Y163L, Y163K, Y163T, S175Y, D219V, and combinations thereof. In certain embodiments of the aforementioned methods where the TNFsf member is human Tumor Necrosis Factor (TNF), the second mutation or bifunctional mutation is selected from the group consisting of L105T, R108F, A160T, V161T, S162A, Q164S, V161S, S162V, S162T, Q164P, T165H, E222T, and T165G and combinations thereof. In certain embodiments of the aforementioned methods where the TNFsf member is human Tumor Necrosis Factor (TNF), the third mutation or bifunctional mutation is selected from the group consisting of L105T, R108F, L151R, A160T, V161T, S162A, S162T, Q164S, T165G, S175Y, E222T, and combinations thereof. In certain embodiments of the aforementioned methods where the TNFsf member is human Tumor Necrosis Factor (TNF), the first mutation or bifunctional mutation is selected from the group consisting of N110Q, L151R, Y163Q, Y163G, Y163L, Y163K, Y163T, S175Y, D219V, and combinations thereof; wherein the second mutation or bifunctional mutation is selected from the group consisting of L105T, R108F, A160T, V161T, S162A, Q164S, V161S, S162V, S162T, Q164P, T165H, E222T, and T165G and combinations thereof; and wherein the third mutation or bifunctional mutation is selected from the group consisting of L105T, R108F, L151R, A160T, V161T, S162A, S162T, Q164S, T165G, S175Y, E222T, and combinations thereof. In certain embodiments of the aforementioned methods, the TNFsf member is TNF-related apoptosis-inducing ligand (TRAIL), the target TNFsf receptor is DR5, and the non-target Tumor Necrosis Factor superfamily receptor is DR4, DcR1, DcR2, and OPG. In certain embodiments of the aforementioned methods where the TNFsf member is TNF-related apoptosis-inducing ligand (TRAIL), the first, second, third, or bifunctional mutations are selected from the TRAIL mutations disclosed in Table 4. In certain embodiments of the aforementioned methods, the TNFsf member is A proliferation inducing ligand (APRIL), the target TNFsf receptor is cyclophilin ligand interactor (TACI), and the non-target Tumor Necrosis Factor superfamily receptor is B cell maturation antigen (BCMA). In certain embodiments of the aforementioned methods where the TNFsf member is APRIL, the first, second, third, or bifunctional mutations are selected from the APRIL mutations disclosed in Table 4. In certain embodiments of the aforementioned methods, the method further comprises an initial step of first obtaining the first mutated TNFsf monomer having the at least one first mutation. In certain embodiments of the aforementioned methods, the obtaining step comprises screening a population of mutagenized TNFsf monomers for at least one first mutation that blocks binding of the TNFsf member consisting of the first mutated monomer to its corresponding target Tumor Necrosis Factor superfamily receptor. In certain embodiments of the aforementioned methods, the method further comprises: (i) obtaining the second mutated TNFsf monomer having the at least one second mutation; or (ii) obtaining a mutated TNFsf monomer comprising the third mutation, or the combination thereof. In certain embodiments of the aforementioned methods, the obtaining step comprises screening a population of mutagenized TNFsf monomers for at least one second mutation or for at least one bifunctional mutation that increases binding affinity of a TNFsf member comprising the second mutated monomer to the corresponding target Tumor Necrosis Factor superfamily receptor. In certain embodiments of the aforementioned methods, the screening comprises detection of binding to limiting amounts of the target TNFsf receptor in the presence of a non-target receptor. In certain embodiments of the aforementioned methods, the obtaining step comprises screening a population of mutagenized TNFsf monomers for at least one third mutation or at least one bifunctional mutation that decreases binding affinity of a TNFsf member comprising monomers with the third mutation to a non-target Tumor Necrosis Factor superfamily receptor. In certain embodiments of the aforementioned methods, iterative selections are used to obtain additional second mutations or bifunctional mutations that increase binding affinity of the TNFsf member comprising the second mutated monomer to the corresponding target Tumor Necrosis Factor superfamily receptor. In certain embodiments of the aforementioned methods, iterative selections are used to obtain third mutations or bifunctional mutations that decrease binding affinity of a TNFsf member comprising the second mutated monomer to a non-target Tumor Necrosis Factor superfamily receptor. In certain embodiments of the aforementioned methods, bifunctional mutations that increase binding affinity to the corresponding target TNFsf receptor while decreasing binding affinity to the corresponding non-target TNFsf receptor are used. In certain embodiments of the aforementioned methods, other bifunctional mutations that reduce or essentially eliminate binding to both the corresponding target TNFsf receptor and the corresponding non-target TNFsf receptor are used. In certain embodiments of the aforementioned methods, the combining step comprises: (i) constructing a recombinant nucleic acid comprising a nucleic acid sequence encoding the first and second mutated monomers, wherein the monomers are operably linked in the encoded single chain polypeptide and wherein the nucleic acid that encodes the single chain polypeptide is operably linked to a promoter, a nucleic acid encoding a signal peptide, or the combination thereof, (ii) introducing the nucleic acid into a cell; and, (iii) harvesting the encoded single chain polypeptide from a cell that comprises the recombinant nucleic acid and expresses the single chain polypeptide or from media in which the cell was grown. In certain embodiments of the aforementioned methods, the monomers are operably linked in the single chain polypeptide with a peptide linker. In certain embodiments of the aforementioned methods, the peptide linker comprises a one or more of a glycine rich peptide, Gly-Gly-Ser-Gly (SEQ ID NO: 38), [Gly-Ser]x linkers where x=2-10; Gly-Gly-Gly-Ser (SEQ ID NO: 39), Gly-Gly-Gly-Gly-Ser (SEQ ID NO: 40); Ser-Glu-Gly; Gly-Ser-Ala-Thr″ (SEQ ID NO: 41), or any combination thereof. In certain embodiments, the peptide linker is about 4 to about 12 amino acids in length. Inhibitors of a Tumor Necrosis Factor superfamily (TNFsf) member receptor that are made by any of the aforementioned methods are also provided herein.

Recombinant single chain polypeptides comprising: (i) at least one mutated TNFsf monomer comprising at least one first mutation that blocks binding of a TNFsf member comprising the first mutated monomer to a corresponding target Tumor Necrosis Factor superfamily receptor; and, (ii) a second mutated TNFsf monomer comprising at least one second mutation that increases binding affinity of a TNFsf member comprising the second mutated monomer to the corresponding target Tumor Necrosis Factor superfamily receptor, wherein a total of at least three mutated TNFsf monomers are operably linked in the recombinant single chain polypeptide and wherein the recombinant single chain polypeptide is an inhibitor of the target Tumor Necrosis Factor superfamily (TNFsf) member receptor are provided herein.

Recombinant single chain polypeptides comprising: (i) at least one mutated TNFsf monomer comprising at least one first mutation that blocks binding of a TNFsf member comprising the first mutated monomer to a corresponding target Tumor Necrosis Factor superfamily receptor; and, (ii) a second mutated TNFsf monomer comprising at least one second mutation that increases binding affinity of a TNFsf member comprising the second mutated monomer to the corresponding target Tumor Necrosis Factor superfamily receptor, wherein a total of at least two mutated TNFsf monomers and a wild-type monomer are operably linked in the recombinant single chain polypeptide, and wherein the recombinant single chain polypeptide is an inhibitor of the target Tumor Necrosis Factor superfamily (TNFsf) member receptor are also provided herein. In certain embodiments, (i) the single chain polypeptide further comprises at least one third mutation in one, two, or three of the monomers that decreases binding affinity of a TNFsf member comprising the monomers with the third mutation to a non-target Tumor Necrosis Factor superfamily receptor; (ii) the second mutation(s) is a bifunctional mutation that both increases binding affinity of a TNFsf member comprising or consisting of the second mutated monomer to the corresponding target Tumor Necrosis Factor superfamily receptor and decreases binding affinity of a TNFsf member comprising or consisting of the second mutated monomer to a non-target Tumor Necrosis Factor superfamily receptor; (iii) the first mutation is a bifunctional mutation that both blocks binding of a TNFsf member comprising or consisting of the first mutated monomer to its corresponding target Tumor Necrosis Factor superfamily receptor and decreases binding affinity of a TNFsf member comprising or consisting of the first mutated monomer to a non-target Tumor Necrosis Factor superfamily receptor; or (iv) the single chain polypeptide comprises any combination of (i), (ii), and (iii). In certain embodiments of any of the aforementioned single chain polypeptides, the single polypeptide chain comprises: (i) two first mutated TNFsf monomers and one second mutated TNFsf monomer; or (ii) the single polypeptide chain comprises one first mutated TNFsf monomer and two second mutated TNFsf monomers. In certain embodiments, bifunctional mutations that increase binding affinity to the corresponding target TNFsf receptor while decreasing binding affinity to the corresponding non-target TNFsf receptor are used. In certain embodiments, other bifunctional mutations that reduce or essentially eliminate binding to both the corresponding target TNFsf receptor and the corresponding non-target TNFsf receptor are used. In certain embodiments of any of the aforementioned single chain polypeptides, the first mutation is selected from the group consisting of an AA″-Loop mutation, a BC loop mutation, a mutation in the C-terminal half of strand C, a CD-Loop mutation, a mutation in the N-terminal half of strand D, a DE Loop mutation, a mutation in the E strand, an EF loop mutation, a mutation in the N-terminal half of strand D, a mutation in the DE loop, an FG loop mutation, a GH-loop mutation, a salt-bridge-disrupting mutation, and combinations thereof, wherein the mutation comprises an insertion, a deletion, a substitution, or a combination thereof. In certain embodiments of any of the aforementioned single chain polypeptides, the TNFsf member is RANKL, the target Tumor Necrosis Factor superfamily receptor is Receptor Activator of Nuclear Factor κ B (RANK), and the non-target Tumor Necrosis Factor superfamily receptor is Osteoprotegerin (OPG). In certain embodiments of the aforementioned single chain polypeptide, the first mutation is selected from the group consisting of a substitution of AA″ loop residues 177-185, R223Q, R223A, R223Y, an insertion immediately C-terminal to R223, H225N, I249R, and combinations thereof; wherein the second mutation or bifunctional mutation is selected from the group consisting of A172R, K195E, F270Y, H271Y, Q237H, Q237T, and combinations thereof; and wherein the third mutation or the bifunctional mutation is selected from the group consisting of G192A, K195E, F270Y, H271Y, Q237H, Q237T, and combinations thereof. In certain embodiments of certain aforementioned single chain polypeptides, the TNFsf member is human Tumor Necrosis Factor (TNF), the target Tumor Necrosis Factor superfamily receptor is Tumor Necrosis Factor Receptor 1 (TNFR1), and the non-target Tumor Necrosis Factor superfamily receptor is Tumor Necrosis Factor Receptor 2 (TNFR2), wherein the first mutation or bifunctional mutation is selected from the group consisting of N110Q, L151R, Y163Q, Y163G, Y163L, Y163K, Y163T, S175Y, D219V, and combinations thereof. In certain embodiments of certain aforementioned single chain polypeptides, the TNFsf member is human Tumor Necrosis Factor (TNF), the target Tumor Necrosis Factor superfamily receptor is Tumor Necrosis Factor Receptor 1 (TNFR1), and the non-target Tumor Necrosis Factor superfamily receptor is Tumor Necrosis Factor Receptor 2 (TNFR2), wherein the second mutation or bifunctional mutation is selected from the group consisting of L105T, R108F, A160T, V161T, S162A, Q164S, V161S, S162V, S162T, Q164P, T165H, E222T, T165G and combinations thereof. In certain embodiments of certain aforementioned single chain polypeptides, the TNFsf member is human Tumor Necrosis Factor (TNF), the target Tumor Necrosis Factor superfamily receptor is Tumor Necrosis Factor Receptor 1 (TNFR1), and the non-target Tumor Necrosis Factor superfamily receptor is Tumor Necrosis Factor Receptor 2 (TNFR2), wherein the third mutation or bifunctional mutation is selected from the group consisting of L105T, R108F, L151R, A160T, V161T, S162A, S162T, Q164S, T165G, S175Y, E222T, and combinations thereof. In certain embodiments of certain aforementioned single chain polypeptides, the TNFsf member is human Tumor Necrosis Factor (TNF), the target Tumor Necrosis Factor superfamily receptor is Tumor Necrosis Factor Receptor 1 (TNFR1), and the non-target Tumor Necrosis Factor superfamily receptor is Tumor Necrosis Factor Receptor 2 (TNFR2), wherein the first mutation or bifunctional mutation is selected from the group consisting of N110Q, L151R, Y163Q, Y163G, Y163L, Y163K, Y163T, S175Y, D219V, and combinations thereof, wherein the second mutation or bifunctional mutation is selected from the group consisting of L105T, R108F, A160T, V161T, S162A, Q164S, V161S, S162V, S162T, Q164P, T165H, E222T, T165G and combinations thereof, and wherein the third mutation or bifunctional mutation is selected from the group consisting of L105T, R108F, L151R, A160T, V161T, S162A, S162T, Q164S, T165G, S175Y, E222T, and combinations thereof. In certain embodiments of certain aforementioned single chain polypeptides, the TNFsf member is human TRAIL, the target Tumor Necrosis Factor superfamily receptor is DR5, and the non-target Tumor Necrosis Factor superfamily receptor is DR4, DcR1, DcR2, and OPG; wherein the first mutation is selected from the group consisting of Y189A, Q193S, N199V, K201R, Y213W, S215D, and combinations thereof; and wherein the second bifunctional mutation is D269H. In certain embodiments of certain aforementioned single chain polypeptides, the TNFsf member is A proliferation inducing ligand (APRIL), the target TNFsf receptor is cyclophilin ligand interactor (TACI), and the non-target Tumor Necrosis Factor superfamily receptor is B cell maturation antigen (BCMA). In certain embodiments of the aforementioned methods where the TNFsf member is APRIL, the first, second, third, or bifunctional mutations are selected from the APRIL mutations disclosed in Table 4. In certain embodiments, the monomers are operably linked in the single chain polypeptide with a peptide linker. In certain embodiments, the peptide linker comprises a one or more of a glycine rich peptide, Gly-Gly-Ser-Gly (SEQ ID NO: 38), [Gly-Ser]x linkers where x=2-10; Gly-Gly-Gly-Ser (SEQ ID NO: 39), Gly-Gly-Gly-Gly-Ser (SEQ ID NO: 40); Ser-Glu-Gly; Gly-Ser-Ala-Thr (SEQ ID NO: 41), or any combination thereof. In certain embodiments, the peptide linker is about 4 to about 12 amino acids in length.

Recombinant nucleic acids that encode any of the aforementioned recombinant single chain polypeptides, wherein the nucleic acid that encodes the single chain polypeptide is operably linked to a promoter, a nucleic acid encoding a signal peptide, or the combination thereof are also provided.

Host cells containing the aforementioned recombinant nucleic acids are also provided.

Methods for producing a recombinant single chain polypeptide inhibitor of a TNFsf member receptor, comprising the steps of: (i) growing the cell of claim 20; and (ii) harvesting the encoded single chain polypeptide from a cell that comprises the recombinant nucleic acid and expresses the single chain polypeptide or from media in which the cell was grown are provided herein.

Composition comprising any of the aforementioned recombinant single chain polypeptides and a pharmaceutically acceptable excipient are provided herein.

Methods for inhibiting bone resorption and/or osteoclastogenesis in a subject in need thereof, comprising the step of administering to the subject a therapeutically effective amount of the aforementioned composition where the TNFsf member is RANKL are provided herein.

Methods of treating osteoporosis in a subject in need thereof, comprising the step of administering to the subject a therapeutically effective amount of the aforementioned composition where the TNFsf member is RANKL are provided.

Methods of treating rheumatoid arthritis, Crohn's disease, psoriasis, psoriatic arthritis (PsA), ulcerative colitis (UC), ankylosing spondylitis, or inflammatory osteolysis in a subject in need thereof, comprising the step of administering to the subject a therapeutically effective amount of the aforementioned composition where the TNFsf member is TNF are provided herein.

Methods of treating a DR5-positive cancer in a subject in need thereof, comprising the step of administering to the subject a therapeutically effective amount of the aforementioned composition, wherein the TNFsf member is TNF-related apoptosis-inducing ligand (TRAIL), either alone or in combination with exogenously added wild-type TRAIL are provided herein.

Methods of treating SLE rheumatoid arthritis or multiple sclerosis in a subject in need thereof, comprising the step of administering to the subject a therapeutically effective amount of the aforementioned composition, wherein the TNFsf member is A proliferation inducing ligand (APRIL) are provided herein.

The present teachings further include the following non-limiting aspects.

1. A RANKL polypeptide encoding three covalently linked monomers of RANKL. 2. A RANKL polypeptide in accordance with aspect 1, wherein the monomers are linked by glycine-rich linkers. 3. A RANKL polypeptide in accordance with aspect 2, wherein the linkers are each G-G-S-G. 4. A RANKL polypeptide in accordance with claim 1, wherein the RANKL polypeptide is a single polypeptide chain (scRANKL). 5. A RANKL polypeptide in accordance with aspect 1, further comprising at least one solubility mutation. 6. A RANKL polypeptide in accordance with aspect 5, wherein the at least one solubility mutation is selected from the group consisting of C220S, E246I, and a combination thereof. 7. A RANKL polypeptide in accordance with aspect 4, further comprising at least one sequence inserted into at least one RANKL loop and/or at least one salt-bridge-disrupting point mutation which forms a single-block scRANKL or a double-block scRANKL. 8. A RANKL polypeptide in accordance with aspect 7, wherein the scRANKL is a single-block scRANKL. 9. A RANKL polypeptide in accordance with aspect 7, wherein the scRANKL is a double-block scRANKL. 10. A RANKL polypeptide in accordance with any of aspects 1-9, further comprising at least one point mutation that increases the affinity of RANKL for a RANK receptor compared to the polypeptide without the point mutation. 11. A RANKL polypeptide in accordance with aspect 10, wherein the at least one point mutation is selected from the group consisting of K194E, Q236H, F269Y, H270Y and a combination thereof. 12. A method of inhibiting bone resorption and/or osteoclastogenesis in a subject in need thereof, comprising, administering to the subject a therapeutically effective amount of a RANKL polypeptide of any of aspects 1-11. 13. A method of treating osteoporosis in a subject in need thereof, comprising: administering to the subject a therapeutically effective amount of a RANKL polypeptide of any of aspects 1-11. 14. A method of generating a RANK inhibitor, comprising: generating at least one first mutation in a RANKL polypeptide using error-prone PCR wherein the at least one first mutation increases affinity for RANK by at least 500-fold; and generating at least one second mutation in the RANKL polypeptide using error-prone PCR wherein the at least one second mutation is a RANK receptor-blocking mutation. 15. A method of generating a TNF inhibitor, comprising: generating at least one first mutation in a TNF using error-prone PCR, wherein the at least one first mutation decreases activation of TNFR1; and generating at least one second mutation in the TNF using error-prone PCR wherein the at least one second mutation decreases inhibition of TNFR2.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

FIG. 1A-FIG. 1D. Construction and validation of single-chain RANKL. (A) Wild-type (WT) homotrimeric RANKL (htRANKL) is assembled from three individual polypeptides (monomers), whereas WT single-chain RANKL (scRANKL) is a single polypeptide containing RANKL monomers that are joined by two [GGSG]x3 amino acid linkers. (B) Coomassie-stained SDS-PAGE gel of WT htRANKL chemically cross-linked by increasing concentrations of BS3. A sample of scRANKL without crosslinking is also shown. 500 ng of each protein was used. n=3 independent experiments. (C) BMMs were incubated in the presence of recombinant WT htRANKL or WT scRANKL as described in the Materials and Methods and the osteoclasts generated were identified by TRAP staining. n=5 independent experiments. (D) Individual monomers of single-block scRANKL or double-block scRANKL were mutated to inhibit their binding to RANK. Thus, single-block scRANKL contains two intact receptor-binding sites, whereas the double-block scRANKL contains one.

FIG. 2A-FIG. 2D. Design of scRANKL variants from mutants that do not bind to RANK. (A) The three labeled loops of RANKL form one side of the RANK-binding interface in the RANK-RANKL co-crystal structure. (9) (B) The binding of the indicated concentrations of WT htRANKL, CDins htRANKL, or GST (a negative control) to RANK-Fc (top) or OPG-Fc (bottom) after incubation for the indicated times was assessed by biolayer interferometry. Curves from triplicate experiments are shown. (C) Top: BMMs were incubated with WT htRANKL or CDins htRANKL (both at 200 ng/ml) and osteoclastogenesis was assessed by TRAP staining. Bottom: BMMs were incubated with WT htRANKL or CDins htRANKL (both at 200 ng/ml) for the indicated times. Cell lysates were then analyzed by Western blotting with antibodies against the indicated proteins to assess IBa phosphorylation. Images and Western blots are representative of three independent experiments. (D) SPR analysis was used to measure the binding of equal amounts of the indicated scRANKL variants coupled to SPR chips to the analyte RANK. Binding curves were generated from triplicate measurements. The average number of RUs for each binding curve at saturation is displayed.

FIG. 3A-FIG. 3D. Generation of high-affinity RANKL mutants by YSD. (A) Histograms showing flow cytometric analysis of the staining of clones with 1 μM monomeric RANK at each phase of library sorting. To select for clones with increased binding to RANK, three rounds of sorting were initiated with a concentration of RANKL that was 10-fold greater than the K_(D) of RANK (Sort #1) and terminated with a concentration of RANKL that was 10-fold less (Sort #3). (B) Point mutants of htRANKL generated by YSD. K_(D) values were estimated by titrating different amounts of RANK with YSD htRANKL and fitting the median fluorescence intensity (MFI) values for RANK binding to a one-site binding model. Values represent the averages of three independent experiments. ND, not enough data points to fit K_(D) values, despite having low amounts of detectable staining at the highest concentrations. The asterisk indicates that the reported affinity of htRANKL for monomeric RANK is 1 μM (9). (C, D) Kinetic and equilibrium affinities of WT htRANKL and KQFH htRANKL for RANK and OPG were determined by SPR measurements. Variants of htRANKL were coupled to a sensor chip and monomeric fragments of RANK or OPG served as analytes. Curve fits of triplicate runs are shown as black lines and values represent means±SD. k_(a) (on-rate), k_(d) (off-rate), K_(D) (equilibrium dissociation constant).

FIG. 4A-FIG. 4F. Development of a competitive antagonist scRANKL. (A) Schematic displaying the mutations incorporated into the single-block, RANK^(high) and double-block, RANK^(high) variants. “X” indicates RANKL variant that does not bind RANK while up arrow indicates RANKL variant with increased affinity for RANK. (B) The relative abilities of WT scRANKL, single-block, RANK^(high) and double-block, RANK^(high) proteins to induce osteoclastogenesis in vitro was determined and quantified by a fluorescent TRAP activity assay. The curve shown is representative of three independent experiments. (C) BMMs were incubated with WT htRANKL or single-block, RANK^(high) for the indicated times. Cell lysates were then analyzed by Western blotting with antibodies against the indicated proteins to determine the phosphorylation of IκBα and p38 MAPK. Western blots are representative of three independent experiments, with IκBα and p38 run in parallel on separate gels. (D) BMMs were incubated with WT htRANKL (200 ng/ml) alone (open diamond) or in the presence of the indicated concentrations of single-block, RANK^(high) (squares) or double-block, RANK^(high) (triangles). The extent of osteoclast formation was determined by measurement of TRAP activity. The curve shown is representative of four independent experiments. (E) BMMs and osteoblasts were co-cultured alone or in the presence of the indicated concentrations of single-block, RANK^(high). Osteoclast numbers were determined by manually counting TRAP-positive multi-nucleated cells. Data are means±SD from three independent experiments. (F) Mice were injected with PBS as a negative control or with WT htRANKL (0.5 mg/kg) alone or together with single-block, RANK^(high) (0.5 mg/kg). Two days later, serum concentrations of CTx were measured by ELISA. Data are means±SD from eight to ten mice per group performed in cohorts of 4-5 mice per group in two independent experiments. Data were analyzed by one-way ANOVA.

FIG. 5A-FIG. 5B. Effect of solubility mutations on RANKL function. (A) SPR assays were performed to determine the kinetic affinities for RANK of WT RANKL and of WT RANKL containing two mutations that increase its solubility (C220S and E246I, WT-SM RANKL). Curves were generated from triplicate samples. Kinetics values beneath the graphs represent means±SD from three independent experiments. (B) BMMs were incubated with the indicated concentrations of WT htRANKL and WT-SM htRANKL, and the extent of osteoclastogenesis was determined by a fluorescent TRAP activity assay. Curves are representative of three independent experiments.

FIG. 6A-FIG. 6B. Comparison of WT htRANKL and scRANKL. (A) MALS analysis of noncovalently linked RANKL (htRANKL) or single-chain RANKL (scRANKL). Because the predominant scRANKL species migrated on a denaturing gel at a position slightly below that of chemically cross-linked htRANKL (FIG. 1B), we calculated the precise molecular mass of htRANKL (left) and scRANKL (right) by MALS. The differences in the calculated and measured molecular masses reflect the presence of substantial glycosylation on these proteins, which are secreted by mammalian cells. Data are representative of three independent experiments. (B) BMMs were incubated with the indicated concentrations of WT htRANKL or WT scRANKL, and the extent of osteoclastogenesis was measured by a colorimetric solution-based TRAP assay. The curves are representative of three independent experiments.

FIG. 7A-FIG. 7D. Selection of RANKL mutants that prevent binding to RANK. (A) The binding of the indicated htRANKL variants to RANK-Fc or OPG-Fc was assessed by BLI. Because of the dimeric nature of the analyte, K_(D) values represent the apparent affinity constants generated from triplicate curves. (B to D) The capacity of the indicated recombinant htRANKL variants to induce osteoclastogenesis in vitro was assessed by (B) TRAP staining, (C) TRAP-solution assay, and (D) real-time PCR analysis of the relative abundances of mRNAs for osteoclastogenic markers. All assays were performed in technical triplicates. Mut16 was selected for incorporation into scRANKL and is highlighted in a red box.

FIG. 8. Ability of scRANKL variants to inhibit WT htRANKL-induced osteoclastogenesis. BMMs were cultured with WT htRANKL (200 ng/ml) and the indicated concentrations of either single-block scRANKL or double-block scRANKL. Four days later, osteoclastogenesis was assessed by TRAP staining. The addition of a monomeric fragment of OPG (4 μg/ml) to cells treated with WT htRANKL was used to demonstrate inhibition of osteoclastogenesis. Images are representative of three independent experiments.

FIG. 9A-FIG. 9D. Reversion mutagenesis of YSD htRANKL clones. (A to D) Yeast cells were induced to express RANKL variants and stained with RANK-Fc (left column in sets of two for each mutant) or OPG-Fc (right column in sets of two for each mutant). The degree of staining detected by flow cytometry was expressed as a percent relative to WT. (A) Top scoring clones from the low (LM3S) or high (HM3S) mutation rate libraries with (B) individual point mutations of these clones. Data are representative of two independent experiments (A and B). (C) A second mutation was added to the most effective individual point mutant (Q236H). (D) A third mutation was added to closely approximate the ideal phenotype. Data are representative of two independent experiments (C and D).

FIG. 10A-FIG. 10C. Identification of htRANKL mutants with prolonged off-rates and decreased binding to OPG by a competitive OPG screen. (A) Representation of the competitive OPG YSD screen. In the context of WT htRANKL (left), RANK (top) fused to a 6×His tag is readily displaced by OPG (bottom left) because of the higher affinity of OPG. Alternatively, in the context of a htRANKL clone that has increased affinity for RANK and that has lost the capacity to bind to the decoy receptor, OPG is incapable of displacing RANK (bottom right). Additionally, only those clones with an increased half-life have sustained binding after washing at room temperature. (B) Individual point mutant htRANKL clones retaining high RANK binding, as detected with a monoclonal antibody against the 6×His tag, after 5 min of competition with OPG. (C) Kinetic competition analysis of the binding of WT htRANKL and the H270Y, KQF, and KQFH htRANKL variants to RANK-6His, in the presence of OPG, based on flow cytometric screening. For (B) and (C), data are expressed as the percentage of htRANKL bound to RANK over time relative to that bound in the absence of OPG. Additionally, the binding of RANK (as detected with an APC-conjugated antibody) was normalized to the amount of htRANKL expressed on the surface of the yeast (as detected with a FITC-conjugated antibody) and expressed as the ratio of the MFIs of the APC and FITC signals. Curves are representative of three independent experiments.

FIG. 11. Effect of htRANKL solubility mutations on binding to OPG. The kinetic affinities of WT-htRANKL and WT-SM htRANKL for OPG were determined by SPR analysis. Curves were generated from triplicate measurements. Values below the plots are means±SD of three independent experiments.

FIG. 12. Van der Waals surface model of WT htRANKL oriented to show the binding cleft. For simplicity, only the two foremost htRANKL monomers are shown; one in gray (darker, right) and the other in white (lighter, left). The RANKL substitution positions selected by YSD are shown in blue. The three residues that can be seen in this view, K194, F269, and Q236, have been labeled. The fourth residue, H270, lies just behind F269. A darkened ribbon model of RANK is shown in the binding cleft, with disulfide bonds inlight lines. Only three of the cysteine-rich domains of RANK are shown. The CD-loop is indicated by a dashed circle.

FIG. 13A-FIG. 13C. Combined mutations of htRANKL that block binding to RANK and OPG. (A) Titration curves of the binding of CDins htRANKL and CDins/Q236H htRANKL to RANK and OPG as assessed by the flow cytometric analysis of yeast cells displaying htRANKL. The binding of RANK or OPG (as detected with APC-conjugated antibodies) was normalized to the amount of htRANKL expressed at the yeast cell surface (as detected with a FITC-conjugated antibody) and was expressed as the ratio of the MFIs of the APC and FITC signals. Curves represent three independent experiments. (B) BMMs were left untreated or were treated with the indicated htRANKL constructs (500 ng/ml) for 5 and 15 min. Cell lysates were then analyzed by Western blotting with antibodies against the indicated proteins. Western blots are representative of three independent experiments. (C) BMMs were incubated with CDins htRANKL or CDins/Q236H htRANKL to generate osteoclasts in vitro at concentrations that were saturating for WT htRANKL (200 ng/ml) or were 10-fold greater (2,000 ng/ml). Images are representative of three independent experiments.

FIG. 14A-FIG. 14B. Effects of single-block, RANK^(high) on cell number and signaling. (A) D2 osteoclasts were left untreated or were incubated with WT htRANKL alone, single-block, RANK^(high) alone, or a combination of both. Cells were then analyzed by MTT assay to determine the effects on cell number. Data are means±SD from three independent experiments and were analyzed by one-way ANOVA. (B) BMMs were left untreated or were pre-incubated for 15 min with single-block, RANK^(high) (500 ng/ml) before being incubated with WT htRANKL (200 ng/ml) or TNF-α (1 ng/ml). Cell lysates were then analyzed by Western blotting with antibodies against the indicated proteins to examine the extent of phosphorylation of IκBα. Western blots are representative of three independent experiments.

FIG. 15A-FIG. 15C. Receptor interfaces in a scTNFsfL. (A) Each scTNFsfL monomer is labeled “A”, “B”, or “C” and is shown connected by the peptide linkers (lines). The interfaces capable of accepting the TNFsf receptor have been arbitrarily named “X”, “Y”, and “Z”. The TNFsf A′A″ and GH loops contribute to the side of the interface termed “L”, and the DE and FG loops contribute to the side termed “R”. Depicted are two possible conformations of scTNFsfL, one that has folded with a right-handed orientation and one folded with a left-handed orientation. The CD and EF loops can contribute to both left and right sides of the interface. The possible interfaces with corresponding contributions from each monomer are indicated below the diagram. (B) Single-block scRANKL provides one example of how individually mutated receptors can yield identical binding interfaces regardless of the right- or left-handed nature of scRANKL folding. *Note that CDins from the “L” side of an interface combined with either a WT or Q236H (“Q”) contributed from the “R” side comprise a receptor blocking interface, while KFH from the “L” side combined with Q from the R side form a high affinity interface. (C) Single-block, RANK^(high) scRANKL interfaces as in (B).

FIG. 16. The structural elements of RANKL (loops and strands) are labeled as described in the original crystal structure (9). The view is directly into the binding site showing both sides of the RANK-binding interface.

DETAILED DESCRIPTION

Provided herein are single chain TNFsf ligands (scTNFsfL) that can effectively antagonize corresponding TNFsf target receptors. In certain embodiments, the scTNFsfL provided herein will selectively inhibit target TNSF receptors while not inhibiting non-target (i.e., decoy) TNFsf receptors. In certain embodiments, the scTNFsfL is a scRANKL comprising a combination of blocked and high-affinity RANK binding sites that inhibits RANK signaling, thus acting as an effective inhibitor of RANKL-mediated osteoclast formation and function. RANKL. RANKL is a member of the TNF superfamily of cytokines, which binds to multiple receptors (RANK and OPG) with different biological effects. In certain embodiments the scTNFsfL provided herein will selectively inhibit a target TNFsf receptor while selectively avoiding non-target (i.e., decoy) receptors that would normally limit the effectiveness against the target receptor. This would have the added benefit of allowing the non-target (i.e., decoy) receptors to continue to inhibit wild-type TNFsfL without interference from the scTNFsfL. In certain embodiments, a single chain RANK ligand (scRANKL) provided herein can comprise a combination of blocking and high affinity mutations which can recognize RANK with high affinity but can fail to recognize osteoprotegerin, thus inhibiting productive and undesirable signaling through RANK by endogenous RANKL while permitting productive and desirable signaling through OPG by endogenous RANKL. Such scRANKL provided herein are useful for inhibiting bone resorption in vivo, and for treating or preventing bone loss diseases such as osteoporosis or inflammatory osteolysis in a human or other mammalian subject. Within the TNFsf, there are several examples of cytokines that demonstrate promiscuity in receptor usage (21). For example, TNF-α, which recognizes both TNFR1 and TNFR2, is central to the pathogenesis of disabling disorders, such as rheumatoid arthritis and psoriasis (22). Indeed, treatment of these diseases has been greatly facilitated by systemic blockade of TNF-α with humanized antibodies or soluble receptor (23, 24). As effective as these drugs are, however, they cause major complications, such as a predisposition to malignancy and serious infections, including tuberculosis (25, 26). Current evidence indicates that the positive effects of anti-TNF-α therapy reflects suppressed activation of TNFR1, whereas the negative consequences are a result of inhibition of the pro-immune properties of TNFR2 (27, 28). TNF and RANKL interact with their receptors in a homologous fashion (9, 10, 29, 30). Provided herein are methods of combining high-affinity mutations and blocking mutations into a single-chain that can be used to construct an effective inhibitor that is receptor-selective. Also provided herein are scTNFsfL and compositions comprising the same as well as methods of using such scTNFsfL and compositions to treat human or animal subjects suffering from disorders where inhibition of corresponding TNFsf receptors is indicated. Also provided herewith are potential mechanisms for blocking TNFR1 stimulation while sparing TNFR2, thereby reducing systemic complications. In principal, a covalently linked system (e.g., a scTNFsfL) offers an advantage over the use of mixed heterotrimers (31) in that the composition of each receptor-binding interface is pre-determined. Indeed, this strategy may be broadly applicable to all members of the pathologically important TNF superfamily.

ABBREVIATIONS

The following abbreviations are used herein.

APC is Allophycocyanin.

BLI is Bio-layer interferometry

BMM are Bone marrow macrophages.

CTx C-terminal telopeptide.

ELISA is Enzyme-linked immunosorbent assay.

FITC is Fluorescein isothiocyanate.

GST is Glutathione S-transferase.

KQF are the K194E, Q236H, F269Y amino acid substitutions in the mouse RANKL monomer amino acid sequence of SEQ ID NO:1.

LPS is Lipopolysaccharide.

MALS is Multi-angle light scattering.

MEM is Minimum essential medium.

MFI is Mean fluorescence intensity.

NCBI is the National Center for Biotechnology Information.

Ni-NTA is Ni-nitrilotriacetic acid.

OPG is Osteoprotegerin.

PBS is Phosphate buffered saline.

PCR is Polymerase chain reaction.

RANK is Receptor activator of NF-kappaB.

RANKL is Receptor activator of NF-kappaB ligand.

RU is Resonance units.

scRANKL is Single-chain Receptor activator of NF-kappaB ligand.

SDS-PAGE is Sodium dodecyl sulfate polyacrylamide gel electrophoresis.

SPR is Surface plasmon resonance

TEV is Tobacco Etch Virus.

TNF is Tumor necrosis factor.

TNFsf is Tumor necrosis factor superfamily.

TRAP is Telomeric repeat amplification protocol.

WT is Wild type.

WT-SM RANKL is Wild type-solubility mutations (i.e., the C220S and I246E amino acid substitutions in the mouse RANKL monomer amino acid sequence of SEQ ID NO: 1 to yield SEQ ID NO:7).

YSD is Yeast Surface Display.

Definitions

As used herein, the phrase “binding affinity” or “affinity” refers to the K_(D) (equilibrium dissociation constant) of ligand and a receptor.

As used herein, the phrases “blocks binding of a TNFsf member” or “blocking mutation(s)” refer to mutations that reduce or essentially eliminate binding of a TNFsf homo-trimer comprising monomers with the mutation to a corresponding target TNFsf receptor in comparison to the binding of a TNFsf homo-trimer comprising wild-type monomers to that same receptor. In certain embodiments, such reductions are at least a two-, three-, four-, five-, seven-, ten, 20-, 50-, or 100-fold reduction in binding affinity of a TNFsf homo-trimer comprising monomers with the mutation to a corresponding target TNFsf receptor in comparison to the binding affinity of a homo-trimer comprising wild-type monomers to the corresponding target TNFsf receptor.

As used herein, the phrase “mutation that increases binding affinity of a TNFsf member comprising the second mutated monomer to the corresponding target Tumor Necrosis Factor superfamily receptor” refers to mutations that increase binding of a TNFsf homo-trimer comprising monomers with the mutations to a corresponding target TNFsf receptor in comparison to the binding of a TNFsf homo-trimer comprising wild-type monomers to that same target TNFsf receptor. In certain embodiments, such binding increases are at least a two-, three-, four-, five-, seven-, ten-fold, 50-fold, 100-fold, or 500-fold increase in binding affinity of the TNFsf homo-trimer comprising monomers with the mutation(s) to a corresponding target TNFsf receptor in comparison to the binding affinity of a homo-trimer comprising wild-type monomers to the corresponding target TNFsf receptor.

As used herein, the phrase “mutation that decreases binding affinity of a TNFsf member comprising the three monomers with the third mutation to a non-target Tumor Necrosis Factor superfamily receptor” refers to mutations that decrease binding of a TNFsf homo-trimer comprising monomers with the mutation(s) to a corresponding non-target TNFsf receptor in comparison to the binding of a TNFsf homo-trimer comprising wild-type monomers to that same non-target receptor. In certain embodiments, such binding decreases are at least a two-, three-, four-, five-, seven-, ten-, 20-, 50-, or 100-fold decrease in binding affinity of the TNFsf homo-trimer comprising monomers with the mutation(s) to a corresponding target TNFsf receptor in comparison to the binding affinity of a homo-trimer comprising wild-type monomers to the corresponding target TNFsf receptor.

As used herein, the phrase “subject in need thereof” refers to a subject in need of a treatment or preventative therapy to address a condition resulting from activity of a target TNFsf receptor in the subject. In certain embodiments, the “subject in need thereof” can be a subject that would benefit from a treatment or preventative therapy that will inhibit a target TNFsf receptor but that will have a reduced or negligible inhibitory effect on a non-target TNFsf receptor.

As used herein, the phrase “effective amount” refers to the amount of a scTNFsfL that is effective in inhibiting a target TNFsf receptor activity in a subject or cell.

As used herein, phrase “pharmaceutically acceptable” is employed herein to refer to those compounds, materials, compositions, and/or dosage forms which are suitable for use in a subject.

The phrase “pharmaceutically-acceptable excipient” as used herein refers to a pharmaceutically-acceptable material, composition or vehicle, such as a liquid or solid filler, diluent, carrier, manufacturing aid (e.g., lubricant, talc magnesium, calcium or zinc stearate, or stearic acid), solvent or encapsulating material, involved in carrying or transporting the therapeutic compound for administration to the subject. Each excipient should be “acceptable” in the sense of being compatible with the other ingredients of the formulation and not injurious to the subject. Pharmaceutically-acceptable excipients include, but are not limited to, amino acids (e.g., glycine, glutamine, asparagine, arginine, or lysine), antimicrobials, antioxidants (e.g., ascorbic acid, sodium sulfite, or sodium hydrogen-sulfite), buffers (e.g., borate, bicarbonate, Tris-HCl, citrates, phosphates, or other organic acids), bulking agents (e.g., mannitol or glycine), chelating agents (e.g., ethylenediamine tetraacetic acid (EDTA)), complexing agents (e.g., caffeine, polyvinylpyrrolidone, beta-cyclodextrin, or hydroxypropyl-beta-cyclodextrin), fillers, monosaccharides, disaccharides, and other carbohydrates (e.g., glucose, mannose, or dextrins), proteins (e.g., serum albumin, gelatin, or immunoglobulins), coloring, flavoring and diluting agents, emulsifying agents, hydrophilic polymers (e.g., polyvinylpyrrolidone), low molecular weight polypeptides, salt-forming counterions (e.g., sodium), preservatives (e.g., benzalkonium chloride, benzoic acid, salicylic acid, thimerosal, phenethyl alcohol, methylparaben, propylparaben, chlorhexidine, sorbic acid, or hydrogen peroxide), solvents (e.g., glycerin, propylene glycol, or polyethylene glycol), sugar alcohols (e.g., mannitol or sorbitol), suspending agents, surfactants or wetting agents (e.g., pluronics; PEG; sorbitan esters; polysorbates e.g., polysorbate 20 or polysorbate 80; triton; tromethamine; lecithin; cholesterol or tyloxapal), stability enhancing agents (e.g., sucrose or sorbitol), tonicity enhancing agents (e.g., alkali m et al halides-preferably sodium or potassium chloride-or mannitol sorbitol), delivery vehicles, diluents, excipients and/or pharmaceutical adjuvants. Other suitable excipients can be found in standard pharmaceutical texts, e.g. in “Remington's Pharmaceutical Sciences”, The Science and Practice of Pharmacy, 19.sup.th Ed. Mack Publishing Company, Easton, Pa., (1995).

As used herein, the phrase “TNF superfamily (TNFsf)” is applied to ligands that fall within this family, their corresponding target receptors, and their non-target receptors (e.g., decoy receptors). Members of the TNFsf, their target receptors, and their non-target receptors are set forth in Table 1.

TABLE 1 TNFsf ligands, target receptors, and non-target receptors. TNFsf Other Non-Target Ligand ligand names Target Receptor Receptor RANKL TNFSF11; RANK OPG ODF; OPGL; sOdf; CD254; OPTB2; TRANCE; hRANKL2 TNF DIF; TNFA; TNFR1 TNFR2 TNFSF2; TNF-alpha TRAIL TL2; APO2L; DR5 DR4 CD253; TNFSF10; Apo-2L 4-1BBL TNFSF9, CD137L APRIL TNFSF13 B cell maturation cyclophilin ligand antigen (BCMA) or interactor (TACI) or cyclophilin ligand B cell maturation interactor (TACT) antigen (BCMA) BAFF TNFSF13B CD27L TNFSF7 CD30L TNFSF8 CD40L TNFSF5 EDA1 EDA-A1 EDA2 EDA-A2 FasL TNFSF6 GITRL TNFS18 LIGHT TNFSF14 Lymphotoxin TNFS1, LTA alpha Lymphotoxin TNFS3 alpha beta OX40L TNFSF4 TL1A TNFSF15 TWEAK TNFSF12

The proteins encoded by the TNFsf members cited in Table 1 and certain mutations in those proteins are at least disclosed in U.S. Pat. No. 8,590,273, which is incorporated herein by reference in its entirety with respect to those sequences and mutations.

As used herein the phrase “operably linked” refers to joining nucleic acid sequences, nucleic acid sequences encoding protein sequences, or protein sequences in a manner that retains the respective functions of each joined sequence. Examples of operable linkage of nucleic acid sequences include, but are not limited to, linkage of promoters to mRNA coding sequences in a manner that provides for transcription of the mRNA under control of the promoter. Examples of operable linkage of nucleic acid sequences encoding protein sequences include, but are not limited to, linkage of a sequence encoding a signal peptide to a protein coding sequence such that the fusion protein will be translated in the correct reading frame and provide for secretion of the protein coding sequence when expressed in a host cell.

To the extent to which any of the preceding definitions is inconsistent with definitions provided in any patent or non-patent reference incorporated herein by reference, any patent or non-patent reference cited herein, or in any patent or non-patent reference found elsewhere, it is understood that the preceding definition will be used herein.

Further Description

Mutations used in the scTNFsfL provided herein can exhibit at least three functional characteristics. A first set of mutations that is used are “blocking mutations” that can reduce or essentially eliminate binding to a corresponding target TNFsf receptor. A second set of mutations that can be used are mutations that can increase binding affinity to the corresponding target TNFsf receptor and are referred to herein as a “second mutation” or “second mutations”. In certain embodiments, a third set of mutations that are used are mutations that can decrease binding affinity to the corresponding non-target TNFsf receptor and are referred to herein as a “third mutation” or “third mutations”. In certain embodiments, bifunctional mutations that both increase binding affinity to the corresponding target TNFsf receptor while decreasing binding affinity to the corresponding non-target TNFsf receptor are used. In certain embodiments, other bifunctional mutations that reduce or essentially eliminate binding to both the corresponding target TNFsf receptor and the corresponding non-target TNFsfreceptor are used. Examples of such bifunctional “blocking mutations” for both a target and a non-target receptor include, but are not limited to, human TNF S175Y or L151R mutations that reduce binding to both TNFR1 and TNFR2 (Table 4). Blocking, second, third, and bifunctional mutations include, but are not limited to, certain mutations or sets of mutations identified in Table 4.

In certain embodiments, the single chain TNFsf ligands (scTNFsfL) provided herein comprise three operably linked TNFsf ligand monomers, where all three monomers are mutated, where one or two of the three monomers contain blocking mutations, and where one or two of the three monomers contain mutations that increase binding affinity for the target TNFsf receptor. In certain embodiments, one, two or three of the monomers can also contain mutations that decrease binding affinity for the non-target TNFsf receptor. In certain embodiments, one, two or three of the monomers can also contain bifunctional mutations.

The binding site for the TNFsf receptor is formed by the interface formed by two adjacent monomers in a scTNFsfL as shown in FIG. 15, which depicts a scRANKL. In certain embodiments, it is desirable to have the blocking and high affinity mutations to be located on the same side of the binding groove. For example, TNFsf monomer AA′, CD, and GH loops contribute to the side of the interface termed “L”, and the TNFsf monomer DE and EF loops contribute to the side termed “R”. Regardless of the orientation of folding (right- or left-handed) of the scTNFsfL, having these mutations occupy the same side of the cleft contributed by each monomer ensures that each interface can be individually mutated (FIG. 15) to provide for a folded scTNFsfL where one or two of the binding sites formed by the monomer interfaces are blocked (i.e., do not bind the target TNSsf receptor) and where one or two of the binding sites formed by the monomer interfaces have increased binding affinity for the target TNSsf receptor. In certain embodiments, this can be achieved by ordering the monomers in the scTNFsfL such that the monomer(s) having the blocking mutations in side “L” are located at the N-terminus of the scTNFsfL and the monomer(s) having mutations that increase binding affinity for the target receptor in side “L” are located at the C-terminus of the scTNFsfL. A non-limiting example of a useful ordering of monomers having blocking mutations and mutations that increase binding affinity for the target receptor is shown in FIG. 15C. In certain embodiments, it is also possible to incorporate mutations that decrease binding affinity for the non-target TNFsf receptor into one, two, or three of the binding interfaces. One illustrative example is provided in FIG. 15 for a scRANKL, where three mutations that increase binding affinity for the target receptor (K194E, F269Y, and H270Y) are on the same side of the interface as the blocking mutation (i.e., side “L” in FIG. 15). In this case a bifunctional mutation (Q236H) that decreases binding affinity for the non target TNFsf receptor (e.g., OPG), is located on the other side of the binding interface (i.e., side “R” in FIG. 15) and can equally participate in the formation of a blocking or a high affinity interaction with the target TNFsf receptor (e.g., RANK) when placed in all three monomers of the scTNFsfL.

The TNFsf ligand monomers containing the mutations can be operably linked in the scTNFsfL with peptide linkers. Such peptide linkers are typically of a length and flexibility that provides for folding of the scTNFsfL to form a trimer with a binding site formed by the monomer interfaces. In certain embodiments, the peptide linker can comprise or consist of one, two, or three, four, five or more “Gly-Gly-Ser-Gly” (SEQ ID NO: 38) units. Other useful peptide linkers that can be used include, but are not limited to: (i) [Gly-Ser]x linkers where x=2-10; (ii) one, two, or three, four, five or more “Gly-Gly-Gly-Ser” (SEQ ID NO: 39) units; (iii) one, two, or three, four, five or more “Gly-Gly-Gly-Gly-Ser” (SEQ ID NO: 40) units; (iv) one, two, or three, four, five or more “Ser-Glu-Gly” units; (v) one, two, or three, four, five or more “Gly-Ser-Ala-Thr” (SEQ ID NO: 41) units; and (vi) any combination of (i)-(v) and/or of one, two, or three, four, five or more “Gly-Gly-Ser-Gly” (SEQ ID NO: 38) units. Without seeking to be limited by theory, it is believed that relatively short peptide linkers of about 4 to about 12 amino acids that include, but not limited to those described above, can provide for recovery of scTNFsfL that preferentially fold in a left-handed configuration (FIG. 15A). Such preferential folding can be desirable in providing for more homogenous populations of scTNFsfL for use in methods of treating subjects suffering from various afflictions and related compositions. Such preferential folding can also be desirable in providing for localization of the desired combinations of blocking mutations, mutations that increase affinity for a target TNFsf receptor, mutations that decrease affinity for a non-target TNFsf receptor in different binding interfaces, and bifunctional mutations (e.g., as shown in FIG. 15).

In certain embodiments, one or more mutations used in the scTNFsfL can be obtained by rational design where one or more residues in structural motifs that have been shown to interact with the target TNFsf receptor are mutated. Structural features common to TNFsf ligands that have been shown to participate in target and non-target receptor binding and that can be targeted for mutagenesis include the AA″ Loop, BC loop, C-terminal half of the C strand, CD Loop, D strand, DE loop, E strand, EF loop, N-terminal half of the F strand, FG loop, and GH loop. Structural studies that detail specific regions and residues in TNFsf ligand interactions with target receptors include, but are not limited to, studies of RANKL and RANK (8, 9, 10, 11); studies of TNF and TNFR1 (29, 30, 31); and studies of TRAIL (Gasparian et al., Apoptosis 2009, 14, 778-787.; Kelley, et al., J Biol Chem 2005, 280, 2205-2212; MacFarlane, et al., Cancer Res 2005, 65, 11265-11270; Tur, et al., J Biol Chem 2008, 283, 20560-20568; Reis et al., Cell Death Dis, 1, e83; van der Sloot, et al., Proc NatlAcad Sci USA 2006, 103, 8634-8639; U.S. Pat. No. 6,740,739). Table 2 provides a non-limiting listing of structural features that can be mutated to provide for blocking mutations, second mutations, third mutations, or bifunctional mutations. Pictorial depictions of these features for RANKL are also provided in FIGS. 2A and 16.

TABLE 2 Structural features of TNFsf monomers that participate in target  and non-target receptor binding TNFsf Human RANKL (SEQ ID  Human TNF (SEQ ID Feature NO: 2) Residue Numbers NO: 4) Residue Numbers AA″ Loop 170-195 95-112 (INATDIPSGSHKVSLSSWYHD (NPQAEGQLQWLNRRANAL) RGWAK) BC loop 210-213 (QDGF) 129-132 (EGLY) C-terminal half  219-224 (NICFRH) 137-142 (QVLFKG) of C strand CD Loop 225-235 (HETSGDLATEY) 143-151 (QGCPSTHVLL) D 237-244 (QLMVYVTK) 152-159 (LTHTISRI) DE loop 245-253 (TSIKIPSSH) 160-164 (AVSYQ) E 254-260 (TLMKGGS) 165-173 (TKVNLLSAI) EF loop 261-270 (TKYWSGNSEF) 174-190 (KSPCQRETPEGAEAKPW) N-terminal half  271-276 (HFYSIN) 191-194 (YEPI) of F FG loop 283-288 (LRSGEE) 202-207 (LEKGDR) GH loop 296-306 (PSLLDPDQDAT) 218-227 (LDFAESGQVY) TNFsf Feature Human TRAIL (SEQ ID NO: 6) Residue Numbers AA″ Loop 125-163 (HITGTRGRSNTLSSPNSKNEK ALGRKINSWESSRSGHSF) BC loop 178-181 (EKGF) C-terminal 186-192 (SQTYFRF) half of C CD Loop 193-205 (QEEIKENTKNDKQ) D 206-212 (MVQYIYK) DE loop 213-219 (YTSYPDP) E 220-227 (ILLMKSAR) EF loop 228-236 (NSCWSKDAE) N-terminal 237-242 (YGLYSI) half of F FG loop 249-254 (ELKEND) GH loop 262-274 (NEHLIDMDHEASF)

Table 3 provides references for the atomic coordinates for RANKL, TNF, TRAIL, their corresponding target receptors, and their corresponding non-target receptors that establish the three-dimensional structures for those molecules. These coordinates can be downloaded from the National Center for Biotechnology Information (NCBI) database on the worldwide web at “ncbi.nlm.nih.gov/pubmed” using the PDB ID provided in Table 3. Structural features described in Table 2 are provided in the structures obtainable from these coordinates. Such three dimensional structures can also be used in the rational design of blocking, affinity increasing, affinity decreasing, and bifunctional mutations that can be used in the scTNFsfL provided herein.

TABLE 3 Structures of TNFsf Ligands target receptors, and non-target receptors. Non- TNFsf Target Target NCBI Ligand Receptor Receptor PDB ID Reference Mouse 1JTZ Lam, J., Nelson, C. A., RANKL Ross, F. P., Teitelbaum, S. L., Fremont, D. H. Journal: (2001) J. Clin. Invest. 108: 971- 979 Mouse 1S55 To be published RANKL Mouse 1IQA Ito, S., Wakabayashi, RANKL K., Ubukata, O., Hayashi, S., Okada, F., Hata, T. Journal: (2002) J. Biol. Chem. 277: 6631- 6636 Mouse 3ME4 Liu, C., Walter, T. S., RANK Huang, P., Zhang, S., Zhu, X., Wu, Y., Wedderburn, L. R., Tang, P., Owens, R. J., Stuart, D. I., Ren, J., Gao, B. Journal: (2010) J. Immunol. Mouse Mouse 4GIQ Nelson, C. A., Warren, RANKL RANK J. T., Wang, M. W., Teitelbaum, S. L., Fremont, D. H. Journal: (2012) Structure 20: 1971-198 Mouse Mouse 3QBQ Ta, H. M., Nguyen, RANKL RANK G. T. T., Jin, H. M., Choi, J. K., Park, H., Kim, N. S., Hwang, H. Y., Kim, K. K. Journal: (2010) Proc. Natl. Acad. Sci. USA 107: 20281-20286 Mouse Mouse 3ME2 Liu, C., Walter, T. S., RANKL RANK Huang, P., Zhang, S., Zhu, X., Wu, Y., Wedderburn, L. R., Tang, P., Owens, R. J., Stuart, D. I., Ren, J., Gao, B. Journal: (2010) J. Immunol. Mouse Mouse 4E4D , J. T., Wang, M. W., RANKL OPG Teitelbaum, S. L., Fremont, D. H. Journal: (2012) Structure 20: 1971-198 Human Human 3URF Luan, X. D., Lu, Q. Y., RANKL OPG Jiang, Y. N., Zhang, S. Y., Wang, Q., Yuan, H. H., Zhao, W. M., Wang, J. W., Wang, X. Q. Journal: (2012) J. Immunol. 189: 245- 252 Mouse 2TNF Baeyens, K. J., De TNF Bondt, H. L., Raeymaekers, A., Fiers, W., De Ranter, C. J. Journal: (1999) Acta Crystallogr., Sect. D 55: 772-778 Human 1TNF Eck, M. J., Sprang, S. R. TNF Journal: (1989) J. Biol. Chem. 264: 17595-17605 Human Human 3ALQ Mukai, Y., Nakamura, TNF TNFR2 T., Yoshikawa, M., Yoshioka, Y., Tsunoda, S. I., Nakagawa, S., Yamagata, Y., Tsutsumi, Y. Journal: (2010) Sci. Signal. 3: ra83-ra83 Human 1TNR Banner, D. W., D'Arcy, TNFR1 A., Janes, W., Gentz, R., Schoenfeld, H. J., Broger, C., Loetscher, H., Lesslauer, W. Journal: (1993) Cell(Cambridge, Mass.) 73: 431-445 Human 1DG6 Hymowitz, S. G., TRAIL O'Connell, M. P., Ultsch, M. H., Hurst, A., Totpal, K., Ashkenazi, A., de Vos, A. M., Kelley, R. F. Journal: (2000) Biochemistry 39: 633- 650 Human 1D2Q Cha, S. S., Kim, M. S., TRAIL Choi, Y. H., Sung, B. J., Shin, N. K., Shin, H. C., ung, Y. C., Oh, B. H. Journal: (1999) Immunity 11: 253-261 Human Human 1D4V Mongkolsapaya, J., TRAIL DR5 Grimes, J. M., Chen, N., Xu, X. N., Stuart, D. I., Jones, E. Y., Screaton, G. R. Journal: (1999) Nat. Struct. Biol. 6: 1048- 1053 Human Human 1D0G Hymowitz, S. G., TRAIL DR5 Christinger, H. W., Fuh, G., Ultsch, M., O'Connell, M., Kelley, R. F., Ashkenazi, A., de Vos, A. M. Journal: (1999) Mol. Cell 4: 563-571 Human Human 1DU3 Cha, S. -S., Sung, B. -J., TRAIL DR5 Kim, Y. A., Song, Y. L., Kim, H. J., Kim, S., Lee, M. S., Oh, B. -H. Journal: (2000) J. Biol. Chem. 275: 31171-31177

In certain embodiments, one or more of the mutations used in the scTNFsfL can be obtained from a previously described TNFsf mutant or a TNFsf mutant provided herein. In certain embodiments, previously and/or instantly described blocking mutations and mutations that increase binding affinity for a target TNFsf receptor can be combined in the scTNFsfL via the methods provided herein to generate effective inhibitors of a given target TNFsf receptor. In certain embodiments, previously and/or instantly described blocking mutations, mutations that increase binding affinity for a target TNFsf receptor, and mutations that decrease binding affinity for a non-target receptor can be combined in the scTNFsfL via the methods provided herein to generate effective inhibitors of a given target TNFsf receptor that have reduced or negligible agonist activity for the non-target TNFsf receptor. In certain embodiments, previously and/or instantly described blocking mutations and bifunctional mutations that decrease binding affinity for a non-target receptor can be combined in the scTNFsfL via the methods provided herein to generate effective inhibitors of a given target TNFsf receptor that have reduced or negligible agonist activity for the non-target TNFsf receptor. Examples of various combinations of previously and/or instantly described blocking mutations, mutations that increase binding affinity for a target TNFsf receptor, mutations that decrease binding affinity for a non-target receptor, and bifunctional mutations include, but are not limited to, those provided in the following table for various scRANKL, scTNF, and scTRAIL.

TABLE 4 Combinations of first blocking mutations, mutations that increase binding affinity for the target receptor, mutations that decrease binding affinity for the non-target receptor, bifunctional mutations that decrease binding affinity for the target receptor and decrease binding affinity for the non-target receptor, and bifunctional mutations that both increase binding affinity for the target receptor and decrease binding affinity for the non-target receptor. Target (T) and Second Third Non-Target mutations that mutations that (NT) First mutations increase reduce (or Receptors that reduce (or binding of a block) binding TNFsf Member Mouse block) binding TNFsf of a TNFsf (SEQ ID NO:; RANK of a TNFsf member to its member to its NCBI) (T) member to its corresponding corresponding Mouse RANKL OPG corresponding target non-target Reference for (NP_035743.2) (NT) target receptor receptor receptor Mutation Set 1  H224N and A171R (U.S. G191A (U.S. U.S. Pat. No. I248R Pat. No. Pat. No. 7,399,829, and FIGS. 29 (U.S. Pat. No. 7,399,829) 7,399,829) and Table 2 disclosed 7,399,829) therein. Set 2  CDins² (an K194E, K194E, FIG. 3, 4, 7 insertion of F269Y, F269Y, GGS after H270Y, and H270Y, and R222 in strand combinations combinations C, yielding thereof.¹ thereof.¹ FR-GGS- Also Q236H.¹ Also Q236H¹. HHET; SEQ ID NO: 44) Set 3  CDins (an Q236H¹ Q236H¹ FIG. 3, 4, 7 insertion of GGS after R222 in strand C, yielding FR-GGS- HHET SEQ ID NO: 44) Set 4  R222Q, or K194E, Q236H¹ FIG. 3, 4, 7 R222A, or F269Y, R222Y, at the H270Y, and end of strand C combinations thereof. Also Q236H¹ Set 5  Swap of AA″ Q236T¹ (U.S. Q236T¹ See FIG. 4 of Lam et loop residues Pat. No. al., 2001, 7(108); 971- SGSHKVSLS 7,399,829) 979. for SSS after U.S. Pat. No. 7,399,829 P175. (Lam et and Table 2 disclosed al.) therein. Second Third mutations that mutations that First mutations increase reduce (or that reduce (or binding of a block) binding block) binding TNFsf of a TNFsf Human of a TNFsf member to its member to its RANKL Human member to its corresponding corresponding (SEQ ID RANK (T) corresponding target non-target NO: 2) OPG (NT) target receptor receptor receptor Set 6  H225N and A172R (U.S. G192A (U.S. U.S. Pat. No. I249R Pat. No. Pat. No. 7,399,829, and FIGS. 29 (U.S. Pat. No. 7,399,829) 7,399,829) and Table 2 disclosed 7,399,829) therein. Set 7  CDins (an K195E, K195E, FIG. 3, 4, 7 insertion of F270Y, F270Y, GGS after H271Y, and H271Y, and R223 in in combinations combinations strand C, thereof.¹ thereof.¹ yielding FR- Also Q237H.¹ Also Q237H.¹ GGS-HHET; SEQ ID NO: 44) Set 8  CDins (an Q237H¹ Q237H¹ FIG. 3, 4, 7 insertion of GGS after R223 in in strand C, yielding FR- GGS-HHET; SEQ ID NO: 44), and also Q237H Set 9  R223Q, or K195E, Q237H¹ FIG. 3, 4, 7 R223A, or F270Y, R223Y, at the H271Y, and end of strand combinations C. Also thereof. Q237H Also Q237H.¹ Set 10 Swap of AA″ Q237T¹ (U.S. Q237T¹ Lam et al., Crystal loop residues Pat. No. structure of the SGSHKVSLS 7,399,829) TRANCE/RANKL for SSS after cytokine reveals P176. (Lam et determinants of receptor- al.) ligand specificity; Journal of Clinical Investigation 2001, 7(108); 971-979. U.S. Pat. No. 7,399,829 on Jul. 15, 2008. and Table 2 disclosed therein. Second Third mutations that mutations that First mutations increase reduce (or that reduce (or binding of a block) binding block) binding TNFsf of a TNFsf TNFR1 of a TNFsf member to its member to its (T) member to its corresponding corresponding Mouse TNFα TNFR2 corresponding target non-target (NP_038721.1) (NT) target receptor receptor receptor Set 11 Y165Q, or S164T¹ S164T¹ See Table 1 of Loetscher Y165G, or (Loetscher et et al., Journal of Y165L, or al.) Biological Chemistry Y165K, or 1993, 35(268): 26350- Y165T. 26357. (Loetscher et al.) Set 12 D221V L108T and L108T and (8) See mutant R1-5 in (Loetscher et R111F¹ R111F¹ Tables 1 and 2 of Mukai al.) (Mukai et al.) et al., Journal of Molecular Biology 2009, (386): 1221-1229. Set 13 S177Y or A162T, A162T, See mutant T8 in Table 2 L153R I163P, I163P, of Shibata et al., Journal (Loetscher et S164A, S164A, of Biological Chemistry al.) Y165I, Y165I, 2008, 2(283): 998-1007. Q166N, Q166N, and E167R.¹ and E167R.¹ (mutant T8, (Shibata et al.) Shibata et al.) Set 14 N113Q L108Q and L108Q and (Loetscher et R111W¹ R111W¹ al.) (mutant R1-2, Mukai et al.) Set 15 Y165Q, A162T, A162T, Y165G, I163T, S164A, I163T, S164A, Y165L, Q166S, and Q166S, Y165K, E167G.¹ and E167G.¹ or Y165T (mutant R1- (Loetscher et 11, Mukai et al.). al.) Second Third mutations that mutations that First mutations increase reduce (or that reduce (or binding of a block) binding block) binding TNFsf of a TNFsf of a TNFsf member to its member to its member to its corresponding corresponding Human TNF TNFR1 (T) corresponding target non-target (SEQ ID NO: 4) TNFR2 (NT) target receptor receptor receptor Comments Set 16 Y163Q, or S162T¹ S162T¹ Y163G, or Y163L, or Y163K, or Y163T. Set 17 D219V L105T and L105T and R108F¹ R108F¹ Set 18 S175Y or A160T, S175Y or L151R¹ V161S, L151R¹ S162V, Q164P, and T165H. Set 19 N110Q L105T, L105T, R108F, and R108F, and E222T¹ E222T¹ Set 20 Y163Q, or A160T, A160T, Y163G, or V161T, V161T, Y163L, or S162A, S162A, Y163K, or Q164S, and Q164S, and Y163T. T165G.¹ T165G.¹ Second Third mutations that mutations that First mutations increase reduce (or that reduce (or binding of a block) binding DR5 (T) block) binding TNFsf of a TNFsf DR4, of a TNFsf member to its member to its Mouse DcR1, member to its corresponding corresponding Trail (SEQ ID DcR2, and corresponding target non-target NO: 5) OPG (NT) target receptor receptor receptor Set 21 Y193A, D279H¹ D279H¹ See Table 2 of Gasparian Q197S, (Gasparian et et al, Apoptosis 2009, S199V, al) (14): 778-787. M205R, Y223W, and S225D. (Gasparian et al) Second Third mutations that mutations that DR4 (T) First mutations increase reduce (or DR5, that reduce (or binding of a block) binding DcR1, block) binding TNFsf of a TNFsf DcR2, of a TNFsf member to its member to its Mouse and member to its corresponding corresponding Trail (SEQ OPG corresponding target non-target ID NO: 5) (NT) target receptor receptor receptor Set 22 Y193N, Q149I, Y193N, See Table 1 Reis et al., R195K, K163R, R195K, Cell Death and Disease Q197R, M205R, Q197R, 2010, 1, e83. H274R, K208H, and H274R, M276L, and S225D. M276L, and D277Q. (mutant 4C7, D277Q. (mutant DR5- Reis et al.) 8, Gasparian et al.) Second Third mutations that mutations that First mutations increase reduce (or DR5(T) that reduce (or binding of a block) binding DR4, block) binding TNFsf of a TNFsf DcR1, of a TNFsf member to its member to its Human DcR2 member to its corresponding corresponding Trail and OPG corresponding target non-target (NP_003801.1) (NT) target receptor receptor receptor Set 23 Y189A, D269H¹ D269H¹ Q193S, N199V, K201R, Y213W, and S215D. Second Third mutations that mutations that First mutations increase reduce (or DR4(T) that reduce (or binding of a block) binding DR5, block) binding TNFsf of a TNFsf DcR1, of a TNFsf member to its member to its Human DcR2, member to its corresponding corresponding Trail and OPG corresponding target non-target (NP_003801.1) (NT) target receptor receptor receptor Set 24 Y189N, G131R, Y189N, R191K, R149I, S159R, R191K, Q193R, N199R, Q193R, H264R, I266L, K201H, and H264R, and D267Q. S215D. I266L, and (mutant DR5- D267Q. 8) Second Third mutations that mutations that First mutations increase reduce (or that reduce (or binding of a block) binding block) binding TNFsf of a TNFsf of a TNFsf member to its member to its Human member to its corresponding corresponding APRIL TACI (T); corresponding target non-target (NP_742085) BCMA (NT) target receptor receptor receptor Set 25 R206E R206M R206M US20140178329 ¹Bifunctional mutations. ²“CDins” refers to an insertion of GGS after R222 in strand C, yielding FR-GGS-HHET (SEQ ID NO: 44) that displaces residues out into the CD loop.

In certain embodiments, one or more of the mutations used in the scTNFsfL can be obtained by a screening assay where TNFsf monomers with desired blocking, second, third, or bifunctional mutations are selected. In certain embodiments, such screening assays can comprise use of a phage, yeast, or other display library comprising a mutagenized population of TNFsf monomers. Such libraries are then screened for the absence or presence of binding to a target TNFsf receptor or, in certain instances, reduced binding to a non-target TNFsf receptor. Binding to target or non-target receptors can be detected through use of either detectably labelled receptors or label-free receptor binding assays. In certain embodiments, TNFsfL with blocking mutations can be identified by screening and selecting for mutations that exhibit reduced binding to the corresponding target receptor. In certain embodiments, TNFsfL with bifunctional blocking mutations that exhibit both reduced binding to the corresponding target receptor and the non-target receptor by either simultaneously or sequentially screening for mutant ligands that exhibit reduced binding to both the corresponding target receptor and the non-target receptor. In certain embodiments, bifunctional mutations that exhibit both increased binding affinity for the corresponding target TNFsf receptor and decreased binding affinity for the corresponding non-target TNFsf receptor can be identified by screening and selecting for mutant TNFsf ligands that exhibit binding to limiting amounts of the target TNFsf receptor in the presence of a TNFsf non-target receptor. In certain embodiments, screening and selecting for mutant TNFsf ligands that exhibit binding to limiting amounts of the target TNFsf receptor in the presence of a TNFsf non-target receptor can be achieved by presenting a labelled target TNFsf receptor in the presence of at least an equimolar or molar excess of an unlabeled non-target receptor. Methods of screening and selecting for TNFsf ligand mutations that provided desired binding properties are disclosed both herein (e.g., in Example 9) and elsewhere.

The scTNFsfL provided herewith can also further comprise additional mutations that confer other desirable properties. In certain embodiments, the TNFsf monomers used in the scTNFsfL can comprise mutations that improve solubility. Examples of mutations that improve solubility of RANKL monomers and scRANKL provided herein include, but are not limited to, I247Q, 1247E, I247K, I247R, and C221S in human RANKL (SEQ ID NO:2). In certain embodiments, the TNFsf monomers used in the scTNFsfL can comprise mutations reduce or eliminate O-linked glycosylation sites by substituting or deleting one or more serine or threonine residues at such sites. In certain embodiments, the TNFsf monomers used in the scTNFsfL can comprise mutations reduce or eliminate N-linked glycosylation sites by substituting, deleting, or otherwise disrupting one or more of such sites. N-linked glycosylation sites will typically comprise the sequence N—X—Y, where N is asparagine, X is any amino acid other than proline, and Y is threonine, serine, or cysteine.

The scTNFsfL provided herein can also be covalently modified. Covalent modifications to the scTNFsfL include, but are not limited to, linkages to polyethylene glycol (“PEG”), polypropylene glycol, and/or polyoxyalkylenes; the alkylation, lipidation, acetylation, and or acylation of one or more side-chains of amino acid residues; the acetylation of an N-terminus; and/or the amidation of a C-terminus. In certain embodiments, such covalent modifications can provide for improved stability, solubility, and/or reduced immunogenicity of the modified scTNFsfL. Such modifications of RANKL are described in U.S. Pat. No. 7,399,829, which is incorporated herein by reference in its entirety, and references disclosed in U.S. Pat. No. 7,399,829.

Non-limiting examples of scTNFsfL provided herein include scRANKL, scTNFL, and scTRAIL. In certain embodiments, the scRANKL is selected from the group consisting of SEQ ID NO: 13, 14, 15, 16, and derivatives thereof. In this context, derivatives of the scRANKL can include, but are not limited to, any of: (i) any of the aforementioned additional mutations that confer other desirable properties or covalent modifications thereof; (ii) a scRANKL having at least 85%, 90%, 95%, 96%, 98%, or 99.5% sequence identity across the entire length of SEQ ID NO: 13, 14, 15, 16 or across the entire length of any of the mutated RANKL monomers contained in SEQ ID NO:13, 14, 15, 16; and (iii) a scRANKL having any of the mutated RANKL monomers contained therein and a different peptide linker or a monomer having at least 85%, 90%, 95%, 96%, 98%, 99.5%, or 100% sequence identity across the entire length of those monomers and a different peptide linker. In certain embodiments, the scTNFL is selected from the group consisting of SEQ ID NO:17, 18, 19, 20, 21, 22, and derivatives thereof. In this context, derivatives of the scTNFL can include, but are not limited to, any of: (i) any of the aforementioned additional mutations that confer other desirable properties or covalent modifications thereof; (ii) a scTNFL having at least 85%, 90%, 95%, 96%, 98%, 99.5%, or 100% sequence identity across the entire length of SEQ ID NO:17, 18, 19, 20, 21, or 22, or across the entire length of any of the mutated TNFL monomers contained therein; and (iii) a scTNFL having any of the mutated TNFL monomers contained in SEQ ID NO:17, 18, 19, 20, 21, or 22 and a different peptide linker or a monomer having at least 85%, 90%, 95%, 96%, 98%, 99.5% sequence identity across the entire length of those monomers and a different peptide linker. In certain embodiments, the scTRAIL is selected from the group consisting of SEQ ID NO:23, 24, 42, 43, and derivatives thereof. In this context, derivatives of the scTRAIL can include, but are not limited to, any of: (i) any of the aforementioned additional mutations that confer other desirable properties or covalent modifications thereof; (ii) a scTRAIL having at least 85%, 90%, 95%, 96%, 98%, 99.5%, or 100% sequence identity across the entire length of SEQ ID NO:23,24, 42, or 43 or across the entire length of any of the mutated TRAIL monomers contained therein; and (iii) a scTRAIL having any of the mutated TRAIL monomers contained in SEQ ID NO:23, 24, 42, or 43 and a different peptide linker or a monomer having at least 85%, 90%, 95%, 96%, 98%, 99.5%, sequence identity across the entire length of those monomers and a different peptide linker. Variants of the RANKL, TNF, and TRAIL sequences provided herewith that can be used in the scRANKL, scTNF, and scTRAIL polypeptides provided herein also include allelic variants of RANK, TNF, and TRAIL monomers that can be accessed from the National Center for Biotechnology Information (NCBI) database on the worldwide web at “ncbi.nlm.nih.gov/pubmed” using the identifiers for those monomers provided in Table 5 and associated links.

The scTNFsfL provided herein can be produced in a transformed cell or organism containing a recombinant nucleic acid where a promoter active in that cell or organism is operably linked to a promoter. Such cells can be prokaryotic or eukaryotic cells (i.e. plant, yeast, fungal, insect, avian, or mammalian cells). Such organisms include, but are not limited to, plants or non-human animals. In certain embodiments, the nucleic acid encoding the scTNFsfL is operably linked to a promoter and a nucleic acid encoding a signal peptide and the scTNFsfL can be secreted from the transformed cell and recovered from the media in which the cell was grown. In other embodiments, the nucleic acid encoding the scTNFsfL is operably linked to a promoter and the scTNFsfL is recovered from the cell. Methods for expressing and recovering the TNFsf member RANKL in prokaryotic cells that can be used to express scRANKL, or adapted for use in expression of other scTNFsfL, are disclosed in U.S. Pat. No. 7,399,829, which is incorporated herein by reference in its entirety. In still other embodiments, the nucleic acid encoding the promoter and the scTNFsfL can be introduced into the genome of a transgenic animal and recovered from the milk of the transgenic animal (e.g., U.S. Pat. Nos. 5,741,957, 5,304,489, and 5,849,992). The scTNFsfL can be purified from the media or from cell lysates by the customary chromatography methods that include, but are not limited to, gel filtration, ion-exchange chromatography, hydrophobic interaction chromatography (HIC, chromatography over DEAE-cellulose or affinity chromatography).

Methods for inhibition of TNFsf receptors in a subject in need thereof by administering an effective amount of a scTNFsfL are also provided herein. The present disclosure also provides specific compositions suitable for such administration that contain scTNFsfL members that include, but are not limited to scRANKL, scTNFL, and scTRAIL, in a subject, including but not limited to, humans and animals. Animal subjects can include companion animals (e.g., cats and dogs) as well as other animals that include but are not limited to, cattle, horses, pigs, sheep, and the like. In certain embodiments, compositions aimed at the treatment of non-human animals, it is anticipated that scTNFsfL member would be derived from the subject animal to minimize immunogenicity of the scTNFsfL

The dosage of scTNFsfL or composition comprising the same that is administered to a subject in need thereof may vary, depending on the reason for use and the individual subject. The dosage may be adjusted based on the subject's weight, the age and health of the subject, genotype, and tolerance for the compound or composition.

The amount of scTNFsfL or composition comprising the same to be used depends on many factors. Dosages may include about 0.1 mg/kg of bodyweight, 0.2 mg/kg of bodyweight, 0.5 mg/kg of bodyweight, 1 mg/kg of bodyweight, 2 mg/kg of bodyweight, about 5 mg/kg of bodyweight, about 10 mg/kg of bodyweight, about 15 mg/kg of bodyweight, about 20 mg/kg of bodyweight, about 25 mg/kg of bodyweight, about 30 mg/kg of bodyweight, about 40 mg/kg of bodyweight, about 50 mg/kg of bodyweight, about 60 mg/kg of bodyweight, about 70 mg/kg of bodyweight, about 80 mg/kg of bodyweight, about 90 mg/kg of bodyweight, or about 100 mg/kg of bodyweight. The scTNFsfL or composition comprising the same can be administered once or multiple times per day. The frequency of administration may vary from a single dose per day to multiple doses per day. Routes of administration of a scTNFsfL or composition comprising the same include oral, parenteral, by inhalation, or topical administration. The term parenteral as used herein includes intravenous, intraarterial, intraperitoneal, intramuscular, subcutaneous, rectal or vaginal administration. In certain embodiments, a form for administration can be a solution for injection, in particular for intravenous or intraarterial injection or drip. In certain embodiments, a suitable pharmaceutical composition for injection may comprise a buffer (e.g. acetate, phosphate or citrate buffer), a surfactant (e.g. polysorbate), optionally a stabilizer agent (e.g. human albumin), etc. However, the scTNFsfL or composition comprising the same can also be delivered directly to the site of the adverse cellular population thereby increasing the exposure of the diseased tissue to the scTNFsfL.

In certain embodiments, the effective amount of the scTNFsfL or composition comprising the same can be administered alone or in combination with one or more additional therapeutic agents (second therapeutic entity), regardless of the disease that said second therapeutic entity is administered to treat. In a combination therapy, the effective amount of the scTNFsfL or composition comprising the same may be administered before, during, or after commencing therapy with another agent, as well as any combination thereof, i.e., before and during, before and after, during and after, or before, during and after commencing the additional therapy.

In certain embodiments, the composition comprises the scTNFsfL. In yet another embodiment, the agent is a nucleic acid that comprises a promoter that is operably linked to a nucleic acid that encodes the scTNFsfL. Delivery methods for other nucleic acids encoding RANKL variants that can be adapted to the scTNFsfL provided herein include, but are not limited to, those described in U.S. Pat. No. 7,399,829, which is incorporated herein by reference in its entirety, and references disclosed in U.S. Pat. No. 7,399,829.

Methods of treating osteoporosis in a subject in need thereof by administering to the subject a therapeutically effective amount of a scRANKL polypeptide, a nucleic acid comprising a promoter that is operably linked to a nucleic acid encoding the scRANKL polypeptide, or compositions comprising the polypeptide or the nucleic acid are provided herein. In certain embodiments, subjects in need of such treatment can be identified by measuring bone mineral density and comparing the values obtained to either a previos measurement in the subject or known values for similar, healthy subjects. In certain embodiments, bone mineral density can be determined by dual x-ray absorptiometry (DXA), quantitative computed tomography (QCT), ultrasonography, single-energy x-ray absorptiometry (SXA), magnetic resonance imaging, radiography, and radiographic absorptiometry. Target subjects include, but are not limited to, postmenopausal woman, malnourished subjects, and others suffering from, or at risk for developing osteoporosis.

Methods for inhibiting bone resorption and/or osteoclastogenesis in a subject in need thereof by administering to the subject a therapeutically effective amount ofa scRANKL polypeptide, a nucleic acid comprising a promoter that is operably linked to a nucleic acid encoding the scRANKL polypeptide, or compositions comprising the polypeptide or the nucleic acid are provided herein. Subjects in need thereof who exhibit excess bone resorption can suffers from the effects of hypercalcemia, have symptoms of hypercalcemia, or exhibit measurable hypercalcemia when compared to either a previous measurement in the subject or known values for similar, healthy subjects. In addition to regulating osteoclast activity, the methods described herein are applicable to inhibiting osteoclast activity, regulating osteoclast generation and inhibiting osteoclast generation in individuals inflicted with excess bone resorption. Osteoclastogenesis can be associated with disease conditions in which there is excess bone remodeling and include, but are not limited to, Paget's disease and cancer. Certain cancers that include, but are not limited to, breast cancer, multiple myeloma, melanomas, lung cancer, prostrate, hematologic, head and neck, and renal cancers, can metastasize to bone, induce bone breakdown by local disrupting normal bone remodeling, and can be associated with enhanced numbers of osteoclasts and enhanced amount of osteoclastic bone resorption resulting in hypercalcemia (US Pat. Appln. Pub. No. 20140178376).

Methods of treating rheumatoid arthritis, Crohn's disease, psoriasis, or inflammatory osteolysis in a subject in need thereof by administering to the subject a therapeutically effective amount of a composition comprising a scTNFL are also provided herein. Biologic TNF.alpha. antagonists, such as infliximab (Remicade®), golimumab (Simponi®), adalimumab (Humira®), and etanercept (Enbrel®) have been shown so far to be efficacious in treating rheumatoid arthritis (RA), psoriatic arthritis (PsA), Crohn's disease (CD), ulcerative colitis (UC), psoriasis, and ankylosing spondylitis (U.S. Pat. Appln. Pub. No. 20150184244). In certain embodiments, the scTNFL ligands provided herein can be used either in place of, or in concert with, those or other TNF antagonists to treat RA, PsA, CD, UC, psoriasis, and/or ankylosing spondylitis. Subjects in need thereof can be identified either by the presence of symptoms or by the presence of certain biomarkers (e.g., U.S. Pat. Appln. Pub. No. 20150184244). In certain embodiments, the scTNFL can preferentially inhibit TNFR1 and exhibit reduced or negligible inhibition of TNFR2 (or the TNFR2-triggered pathways), resulting in a reduction in undesirable side effects associated with TNF antagonists that non-selectively inhibit both TNFR1 and TNFR2. Anticipated reductions in side effects associated with certain scTNFL provided herein include, but are not limited to, reduced immune function resulting in increased susceptibility to infections. Methods of treating a DR5-positive cancer in a subject in need thereof by administering to the subject a therapeutically effective amount of the composition comprising a scTRAIL, either alone or in combination with exogenously added wild-type TRAIL, or also provided herein. In certain embodiments, the scTRAIL provided herein can induce apoptosis in cancer cells (e.g., DR5-positive cancer cells, DR5-positive cancer cells that over express or have higher levels of DR5 activity, and the like). It is contemplated that scTRAIL provided herein can be employed to treat cancer cells either in vivo or ex vivo. Ex vivo treatments can be used in bone marrow transplantation and particularly, autologous bone marrow transplantation. Ex vivo treatments described in U.S. Pat. No. 6,740,739, which is incorporated herein by reference in its entirety, can be adapted for use with the scTRAIL provided herein.

Methods of treating systemic lupus erythematosus (SLE) rheumatoid arthritis or multiple sclerosis in a subject in need thereof, comprising the step of administering to the subject a therapeutically effective amount of the aforementioned composition, wherein the TNFsf member is A proliferation inducing ligand (APRIL) are also provided herein. Certain inhibitors of TACI likely block both APRIL and BAFF signaling. Ataicicept (a TACI-Ig fusion protein) was found to be considerably safe and well tolerated in patients with rheumatoid arthritis, with some evidence of biological activity. But, primary endpoints were not met in Phase II trials (van Vollenhoven et al., 2011; Arthritis Rheum. 63(7):1782-92). A more active inhibitor of this pathway could prove beneficial. Methods and APRIL mutants disclosed in US Patent Pub. 20140178329, which is incorporated herein by reference in its entirety, can be adapted for use in the methods and compositions involving scAPRIL that are provided herein.

EXAMPLES Example 1. Identification of RANKL Mutants which do not Bind RANK

RANKL residues forming salt bridges or hydrogen bonds with RANK were targeted for site directed mutagenesis using the program PISA (European Bioinformatics Institute, Cambridgeshire, UK) and the RANK/RANKL co-crystal structure (9). Loops at the RANK/RANKL interface were disrupted by amino acid insertion. Mutations were introduced into the expression construct, pGEX-GST-RANKL, by PCR using Phusion polymerase (New England BioLabs, Ipswich, Mass.). After verification by nucleic acid sequencing, the mutant RANKL-encoding constructs were transformed into E. coli strain BL21-CodonPlus (DE3)-RIL competent cells (Agilent Technologies Inc., Santa Clara, Calif.) for protein production. Correctly-folded soluble protein was purified from cell lysate on glutathione sepharose (8). The mutant RANKL protein was released from the GST affinity tag by digestion with PreScission™ protease (GE Life Sciences, Piscataway, N.J.).

Example 2. Development of RANKL Variants

We covalently linked three RANKL monomers with two short glycine-rich linkers (FIG. 1A), which were modeled after previously reported single-chain versions of other TNF superfamily members (13-16). This version of RANKL encoded as a single-chain (scRANKL) protein enabled individual modification of the binding affinities of the three binding sites for RANK and OPG. We refer to the noncovalently linked, homotrimeric version of RANKL as “htRANKL.” Two additional surface “solubility” mutations Cys²²⁰→Ser and Ile²⁴⁶→Glu (C220S/I246E), which do not affect the binding of the mutant RANKL to RANK or its function, were introduced to improve protein production (FIGS. 5, A and B). This version of RANKL is referred to as “WT-SM htRANKL.” Therefore, all versions of htRANKL and scRANKL incorporate these two solubility mutations. As expected, no monomeric species of scRANKL was observable on a denaturing gel (FIG. 1B), and scRANKL migrated similarly to the trimeric species of chemically cross-linked wild-type htRANKL. To avoid potential discrepancies in molecular mass when comparing the cross-linked protein to the native protein, we more precisely determined the molecular masses of htRANKL and scRANKL by multi-angle light scattering (MALS) analysis. We found that scRANKL had a molecular mass consistent with that of three covalently linked RANKL monomers (FIG. 6A). Moreover, scRANKL induced bone marrow macrophages (BMMs) to undergo osteoclastogenesis as effectively as did the wild-type cytokine (FIG. 1C and FIG. 6B).

Example 3. Development of scRANKL Constructs that Block Receptor Recruitment

To engineer scRANKL constructs that blocked receptor binding at one site (“single-block scRANKL”) or two sites (“double-block scRANKL”, FIG. 1D), we inserted short sequences into several loops of RANKL (FIG. 2A) or introduced point mutations that disrupted salt bridge formation (FIG. 7). One mutant, in which three amino acid residues (Gly-Gly-Ser) were inserted into the c-terminal end of strand C after residue 222 (CDins htRANKL), failed to bind to a recombinant fusion protein of Fc and RANK (RANK-Fc) despite undergoing proper folding, as established by its ability to bind to OPG-Fc in a dose-dependent manner (FIG. 2B). Consistent with its failure to bind to RANK, the CDins htRANKL mutant was incapable of inducing osteoclast formation or promoting RANK signaling in bone marrow macrophages (BMMs) (FIG. 2C). Next, we generated single-block and double-block scRANKL mutants by inserting CDins into one or two monomers, respectively, of the single-chain trimer. We compared the degree of receptor binding at saturation by flowing monomeric RANK, as an analyte, over a surface plasmon resonance (SPR) chip. As expected, blocking each binding site diminished receptor recognition by approximately one-third (FIG. 2D).

Having developed scRANKL variants that had an altered capacity to initiate trimeric receptor clustering, which is presumed to be required for optimal signaling, yet retained the ability to bind to RANK, we postulated that these proteins might act as inhibitors of osteoclastogenesis induced by wild-type htRANKL; however, this proved not to be the case (FIG. 8). This lack of inhibitory ability likely reflected the failure of the one (or two) intact binding site(s) to overcome the avidity afforded by the three sites of wild-type htRANKL. We reasoned that we might increase the inhibitory effectiveness by compensating for the reduced avidity of single-block or double-block scRANKL through increasing the affinity for RANK at the intact site(s). This required identifying previously uncharacterized RANKL mutations that increased its affinity for RANK.

Example 4. Two Generations of In Vitro Evolution Through Yeast Surface Display Identifying Previously Uncharacterized RANKL Mutations that Increased its Affinity for RANK

To identify RANKL mutations that increase affinity for RANK, we performed two generations of in vitro affinity maturation through yeast surface display (YSD) (17). The first round involved creating a library of htRANKL mutants through error-prone polymerase chain reaction (PCR) assays and sorting for clones that retained the ability to bind to RANK-Fc. Notably, OPG, the principal biological inhibitor of RANK-induced osteoclastogenesis (18-20), exerts its effects by competing with RANK for binding to RANKL. Because both RANK and OPG bind to the same groove of RANKL, it is possible that increasing the affinity of RANKL for RANK could simultaneously increase its binding to the decoy receptor. To obviate this possibility, we simultaneously sorted the library for clones with higher affinity for RANK and with decreased affinity for OPG-Fc (FIG. 9A). Reversion mutagenesis yielded individual point mutations (K194N, Q236H, F269Y) in htRANKL which, when expressed in combination (KQF), substantially increased the affinity of the mutant htRANKL for RANK-Fc while decreasing its affinity for OPG-Fc (FIGS. 9, B C, and D).

In the second generation of in vitro evolution, we selected htRANKL variants with long RANK kinetic half-lives. We again constructed an htRANKL mutant library through error-prone PCR, but this time used the high-affinity KQF htRANKL mutant as a starting template. Because of its rapid off-rate, monomeric RANK did not stain yeast-displayed wild-type htRANKL, despite their established interaction (FIG. 3A). We therefore sorted the second library with sequentially limiting amounts of monomeric RANK. This sorting strategy yielded a population of htRANKL variants that were capable of binding monomeric RANK (FIG. 3A).

Example 5. Identification of an Additional RANKL Point Mutation and Development of RANKL Variants Including the Additional Point Mutation

We next selected htRANKL variants that continued to bind to limiting amounts of RANK after incubation in the presence of unlabeled OPG for 5 min at room temperature (FIG. 10). We identified several additional mutations at residue K194 and chose to use the K194E mutation going forward in KQF htRANKL, because the K194N mutation introduced a potential N-linked glycosylation site that could confound results when comparing proteins produced by yeast and mammalian cells. These strategies also yielded the htRANKL point mutant (H270Y), which, when incorporated into the KQF htRANKL mutant, further increased its affinity for RANK without yielding detectable binding to OPG (FIG. 3B). We then determined the affinities and kinetic parameters of the RANKL variant that showed the greatest binding to RANK by SPR (FIG. 3C). Although the two solubility mutations that were introduced to produce scRANKL had no effect on RANK binding, they resulted in an approximately ten-fold decrease in binding to OPG (FIG. 11). The KQFH htRANKL variant bound to RANK with an approximately 500-fold greater affinity than did wild-type htRANKL; however, it exhibited substantially impaired binding to OPG (FIG. 3B). These changes in affinity for RANK largely reflected a prolonged half-life of binding, changing from a relatively rapid dissociation time (t_(1/2)=3 s for WT htRANKL) to a dissociation time that was more than 200-times longer (t_(1/2)=675 s for KQFH htRANKL). The KQFH mutations cluster in two regions of RANKL that were previously implicated in binding to RANK (9) (FIG. 12). To ensure that the RANK-blocking interface would also block binding to OPG, we combined CDins with the Q236H mutation, because Gln²⁶ was identified by YSD as the amino acid residue responsible for decreased binding to OPG. Indeed, we confirmed that the variant RANKL that combined CDins with the Q236H mutation did not bind to RANK (FIG. 13).

Example 6. Generation of an Inhibitor of RANKL-Mediated Signaling

To generate an effective inhibitor of RANKL-mediated signaling, we incorporated the high-affinity KQFH variant (RANK^(high)) into our single-block and double-block constructs (FIG. 4A). Before determining the capacity of these scRANKL variants to act as inhibitors of RANKL-RANK signaling, we assessed their capacity to generate osteoclasts. Both the single-block and double-block scRANKL variants that had increased affinity for RANK (single-block, RANK^(high) and double-block, RANK^(high)) were incapable of generating osteoclasts in vitro (FIG. 4B). Concurrently, we observed a lack of associated signals induced by the single-block, RANK^(high) variant (FIG. 4C). In contrast to the failure of single-block or double-block scRANKL containing unaltered residual monomer(s) to inhibit RANK signaling and osteoclast formation, the double-block, RANK^(high) scRANKL variant effectively inhibited signaling stimulated by wild-type htRANKL with an IC₅₀ of ˜10 nM (FIG. 4D). The potency of inhibition increased (resulting in an IC₅₀ of 0.2 nM) when two sites were available to bind RANK with high affinity (single-block, RANK^(high)), and this effect was not attributable to cytotoxic effects (FIG. 14A). Additionally, blockade was specific for RANK-mediated signaling, because TNF receptor 1 (TNFR1)-mediated phosphorylation of inhibitor of κB α (IκBα) downstream of TNF-α was not blocked by the single-block, RANK^(high) variant (FIG. 14B). The inhibitory effects of the single-block, RANK^(high) variant were not limited to exogenous wild-type htRANKL, because it also dose-dependently inhibited osteoclast formation induced by htRANKL produced by osteoblasts (FIG. 4E).

Example 7. Intraperitoneal scRANKL Injection

We tested the effectiveness of the single-block, RANK^(high) variant at blocking recombinant wild-type htRANKL-induced osteoclastic bone resorption in vivo.

Intraperitoneal injection of recombinant wild-type htRANKL into 8-week old BALB/c mice increased osteoclast function as determined by measuring serum carboxy-terminal collagen crosslinks (CTx), a marker of bone resorption (FIG. 4F). This increase in bone resorption was completely abrogated by the addition of an equal amount of the single-block, RANK^(high) variant, which suggests that this inhibitor may have therapeutic potential.

Example 8. Development of a scTNFL Variant

A TNF variant is developed using a strategy of combining high affinity and blocking mutations into a single-chain construct. An effective inhibitor that is receptor selective is produced. This TNF variant inhibitor can block TNFR1 while sparing TNFR2, thereby reducing systemic complications.

Example 9. Materials and Methods Used

Construction of an scRANKL Vector and Cloning of cDNAs Encoding scRANKL, htRANKL, and TNF-α into a Mammalian Expression Vector

Initially, the cDNA encoding scRANKL was cloned into the pGEX vector (GE-Healthcare) by PCR-based amplification of the coding sequence of the mouse RANKL monomer (including amino acid residues 162 to 316 of NCBI Reference Sequence NP_035743) with primer pairs that inserted the following restriction enzyme sites: 5′-Sma I-RANKL-Bsp EI-3′, 5′-Bsp EI-RANKL-Bam HI-3′, and 5′-Bam HI-RANKL-Not I-3′. The primers were designed such that the three monomers are separated by a linker sequence [(Gly-Gly-Ser-Gly]×3). Each insert was double-digested with the appropriate restriction enzymes (Fermentas) and ligated into the pGEX vector between the Sma I and Not I sites. The entire scRANKL cDNA was subcloned into the mammalian protein expression vector pFM (32) (gift of Dr. Filipo Mancia) downstream of the signal peptide from pHLsec (MGILPSPGMPALLSLVSLLSVLLMGCVA; SEQ ID NO:25) (33). To aid protein recovery, a tobacco etch virus (TEV) protease cleavage site and a 6×-histidine tag were added at the C-terminus (SSGRENLYFQGHHHHHH; SEQ ID NO:26). The 6×-histidine tag can be removed by TEV cleavage to yield the sequence SSGRENLYFQ (SEQ ID NO:27) at the C-terminus of the recovered protein. In brief, the construct encodes: a signal-peptide, RANKL (residues 162 to 316), a linker, RANKL (residues 162 to 316), a linker, RANKL (residues 162 to 316), a TEV cleavage site, and the 6×His tag. Expression of the construct is driven by the CMV promoter. Transfection efficiency was monitored by detection of red fluorescent protein, whose expression is initiated downstream of scRANKL at an internal ribosomal entry site. To clone the cDNA encoding htRANKL into the pFM mammalian expression vector, the cDNA sequence encoding amino acid residues 162 to 316 was amplified, digested with the restriction enzymes Bsu 361 and Sal I, and ligated downstream of the pHLsec signal peptide and upstream of the TEV cleavage site. To clone the cDNA encoding murine TNF-α, the cDNA sequence encoding amino acid residues 90 to 325 was amplified by overlap extension PCR to add a 5′ pHLsec signal peptide site and a 3′ Sal I restriction site. The cDNA was digested with Xba I and Sal I and ligated downstream of the CMV promoter and upstream of the TEV cleavage site.

Production of Mammalian RANKL and TNF-α Proteins

Suspension-adapted 293-Freestyle cells (Life Technologies) were maintained in serum-free Freestyle 293 expression medium (Life Technologies) according to the manufacturer's protocol. For transfection, DNA was prepared with an endotoxin-free maxiprep kit (Qiagen). Cells were seeded at a density of 0.5×10⁶/ml in 200 ml of medium 24 hours before transfection. On the day of transfection, DNA and polyethylenimine (33) were mixed at a ratio of 1:3 (htRANKL or TNF-α, 200 ρg:600 μg) or 1:2 (scRANKL variants, 200 μg:400 μg) in opti-mem (Life Technologies), incubated for 15 min at room temperature, and added directly to the cells. Cell culture medium was harvested four and seven days after transfection, filtered through a 0.22-μm filter, and equilibrated by the addition of 0.1 volume of 10× phosphate-buffered saline (PBS, Gibco) and 10 mM imidazole. The protein was captured on Ni-NTA Superflow resin (Qiagen) and washed with 10 mM imidazole in PBS. Protein was eluted in steps from 25 to 500 mM imidazole. Fractions containing purified protein were identified by coomassie stained SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Protein-containing fractions were pooled and concentrated with a disposable YM30 centricon (Millipore). All proteins were sterile-filtered for use in cell culture. Only lipopolysaccharide (LPS)-free plastics and reagents were used for all purifications.

SPR Measurements

All SPR experiments were performed on a Biacore T-100 (GE Healthcare) with CM5 sensor chips and HBS-EP buffer (10 mM HEPES (pH 7.4), 150 mM NaCl, 3 mM EDTA, and 0.05% v/v Surfactant P20). To confirm receptor binding to scRANKL variants, 4,000 response units (RU) of wild-type (WT) scRANKL or variant scRANKL were coupled to individual lanes, leaving one reference flow cell uncoupled. Monomeric RANK (20 μM) was flowed over until saturation. Total RUs bound at equilibrium were calculated with BIAEvaluation software. Experiments to determine kinetic affinity constants of RANKL variants for RANK or OPG were performed and analyzed as previously described (9).

Generation of Osteoclasts from Primary Bone Marrow-Derived Macrophages

Long bones isolated from eight week-old mice were flushed, and the marrow was subjected to red blood cell lysis. The remainder of the whole marrow was cultured on petri dishes or bone powder as previously described (34), maintained at 37° C. and 6% CO₂ in α-MEM medium containing 10% heat-inactivated f et al bovine serum (FBS), penicillin (100 U/ml), streptomycin (100 μg/ml), (α-10 medium) supplemented with 1:10 CMG [conditioned medium supernatant containing recombinant M-CSF (macrophage colony-stimulating factor)](35). Osteoclasts were differentiated in α-10 medium with 1:50 CMG and the relevant RANKL variant.

Detection of Osteoclast Formation

Cells were fixed in 4% paraformaldehyde in PBS for 15 min and stained for tartrate-resistant acid phosphatase (TRAP) with a specific kit (Sigma). Additionally, osteoclasts were quantified by a solution assay of TRAP enzyme activity. Cells were fixed and lysed in 90 mM citrate buffer (pH 5.2), 80 mM sodium tartrate, 0.1% Triton-X-100 for 10 min at room temperature. Colorimetric nitrophenylphosphate (a substrate of TRAP) was added and visualized after 15 min by the addition of sodium hydroxide. Data were acquired with the 405-nM absorbance filter on a Bio-rad plate reader. Because of the limited range of the TRAP solution assay, a more quantitative assessment of TRAP activity was performed with the fluorescent phosphatase substrate ELF-97 (Molecular Probes). Fixed cells were incubated with 100 μM ELF-97 in 90 mM citrate buffer (pH 4.8), 80 mM sodium tartrate for 15 min at room temperature. The reaction was stopped by the addition of sodium hydroxide, and fluorescence was visualized with the 345/530 excitation/emission filter on a Spectramax M2 plate reader.

Multi-Angle Light Scattering (MALS) Analysis

Purified RANKL proteins were applied to a Wyatt WTC-030S5 size-exclusion column mounted on a Waters HPLC system attached to a multi-angle light scattering (MALS) device. The light detectors, a Dawn HELEOS-II 18-angle light scattering detector and an Optilab rEX refractive index, were previously calibrated against monomeric bovine serum albumin. MALS was monitored during the experiments, and the resulting data were analyzed with associated software. For each experiment, 250 μg of sample was applied at a concentration of 1 mg/ml in running buffer [25 mM hepes (pH 7.4), 150 mM NaCl, 0.01% sodium azide) at 20° C. and a flow rate of 0.5 ml per minute.

Chemical Cross-Linking

Purified WT-RANKL protein (500 ng) was incubated with varying concentrations (0 to 500 μM) of the chemical cross-linker bis-(sulfosuccinimidyl)-suberate (BS³, Pierce) in PBS at room temperature for 30 min, at which time the reaction was stopped by the addition of 10 mM Tris-HCl (pH 7.0). Samples were boiled under reducing conditions and loaded onto SDS-PAGE gels (10%) alongside 500 ng of scRANKL protein. Bands were stained with the coomassie derivative Imperial protein stain (Pierce) and visualized with the Odyssey scanner (Licor).

Identification of RANKL Mutants that Did not Bind to RANK

RANKL residues forming salt bridges or hydrogen bonds with RANK were targeted for site-directed mutagenesis with PISA software based on the RANK-RANKL co-crystal structure (9). Loops at the RANK-RANKL binding interface were disrupted by amino acid insertion. Mutations were introduced into the expression construct, pGEX-GST-RANKL, by PCR with Phusion™ polymerase (NEB). The constructs were verified by nucleic acid sequencing. Escherichia coli strain BL21-CodonPlus (DE3)-RIL competent cells (Agilent Technologies) were transformed with the mutant RANKL-encoding constructs to generate proteins. Correctly folded soluble proteins were purified from cell lysates on glutathione sepharose (8).

Bio-Layer Interferometry (BLI)

All BLI experiments were performed on an Octet RED™ system (ForteBio). Glutathione-S-transferase (GST)-RANKL fusion proteins were biotinylated with NHS-PEG4-biotin (Pierce) according to the manufacturer's protocol, and excess biotin was removed by desalting over Zeba™ Spin Columns (7-kD molecular mass cutoff, Pierce). Biotinylated proteins were adsorbed onto super-streptavidin sensor pins (ForteBio). Binding of RANK-Fc or OPG-Fc was measured in HBS-EP containing 1% BSA. Because of the dimeric nature of Fc-tagged receptors, only apparent K_(D) values were observed.

Quantitative Real-Time PCR Analysis

To quantitate the abundances of mRNAs for markers of osteoclast formation, total RNA was isolated from cultured cells with the Qiagen RNeasy™ miniprep kit according to the manufacturer's protocol. Equal amounts of RNA were used to perform reverse transcription with Bio-rad iScript™, and quantitative real-time PCR analysis was performed with a SsoFast EvaGreen™ qPCR kit (Bio-Rad) with a 7500 fast machine (ABI). Cyclophilin was used as the housekeeping control gene. Data were analyzed according to the ΔΔCt method, and expressed relative to a control containing no RANKL addition (labeled BMM). The primers used were as follows: Cathepsin K (Forward: 5′-ATGTGGGTGTTCAAGTTTCTGC-3′ (SEQ ID NO:28), Reverse: 5′-CCACAAGATTCTGGGGACTC-3′), SEQ ID NO:29); NFATcl (Forward: 5′-CCCGTCACATTCTGGTCCAT-3′, SEQ ID NO:30); Reverse: 5′-CAAGTAACCGTGTAGCTGCACAA-3′ (SEQ ID NO:31), TRAP (Forward: 5′-CAGCTCCCTAGAAGATGGATTCAT-3′, SEQ ID NO:32, Reverse: 5′GTCAGGAGTGGGAGCCATATG (SEQ ID NO:33), 33 (Forward: 5′-TTCGACTACGGCCAGATGATT-3′, SEQ ID NO:34) Reverse: 5′-GGAGAAAGACAGGTCCATCAAGT-3′ (SEQ ID NO:35) and Cyclophilin (Forward: 5′ AGCATACAGGTCCTGGCATC-3′, SEQ ID NO:36); Reverse: 5-TTCACCTTCCCAAAGACCAC-3′; SEQ ID NO:37).

Western Blotting

Cells were washed three times in ice-cold PBS and lysed with RIPA buffer (Millipore) supplemented with protease and phosphatase inhibitor cocktail (Pierce). After 10 min of incubation on ice, cell lysates were cleared of debris by centrifugation for 15 min at 21,000 g. Forty to fifty micrograms of protein were resolved by 10% SDS-PAGE, transferred onto polyvinylidene difluoride (PVDF) membranes, and incubated with primary antibody overnight. After extensive washing and incubation with near-infrared-labeled secondary antibody, membranes were visualized with the Odyssey scanner (Licor). Primary antibodies to detect phosphorylated or total NF-κB or p38 MAPK proteins were obtained from Cell Signaling; antibody against actin was from Sigma; and fluorescently labeled secondary antibodies were obtained from Rockland.

YSD of RANKL and Flow Cytometric Staining with Monomeric RANK or OPG

The cDNA encoding WT-SM RANKL was subcloned into the pYD1 yeast display vector (Life Technologies) at the Nhe I and Xho I restriction sites to generate the yeast mating protein Aga2p fused to the RANKL N-terminus and having a V5-epitope tag at the C-terminus. EBY100 yeast cells were transformed with the pYD1-RANKL construct using the lithium acetate/single-stranded DNA method as described (36) and colonies were selected in tryptophan-deficient, glucose-based medium at 30° C. Display of RANKL protein was induced by inoculating into galactose-based selective medium and incubating at 30° C. with shaking for 24 to 48 hours. Surface expression of RANKL was detected with a fluorescein isothiocyanate (FITC)-conjugated anti-V5 antibody (Invitrogen). After incubation with RANK-Fc or OPG-Fc for 10 min at room temperature and washing with ice-cold PBS, receptor binding was detected with an allophycocyanin (APC)-conjugated anti-human Fc antibody (Molecular Probes). All experiments were performed with LSR II or Canto II flow cytometers (BD Biosciences) and data were analyzed with the FlowJo™ software package (Tree Star, Inc.). Alternatively, RANK-6×His or OPG-6×His proteins were detected with APC-labeled anti-6×His antibody (MBL International).

Generation of RANKL Library and Selection

Primers annealing immediately 5′ or 3′ to the cDNA sequence encoding RANKL in the pYD1 vector were designed and used in error-prone PCR amplification (Gene Morph II, Agilent). Lower and higher mutation rates were accomplished by manipulating the amount of starting template and the number of amplification cycles. The resulting product was further amplified with the high-fidelity Phusion polymerase (Finnzymes). Simultaneously, the pYD1 vector backbone was amplified with primers that extended outward from the regions surrounding RANKL-V5, leaving 24 base pairs of overlap between the vector backbone and the amplified mutant RANKL-V5 insert. These purified PCR products were used in the transformation of EBY100 cells according to established protocols (36), which yielded a library of approximately 1×10⁶ transformants. Selections were made with magnetic assisted cell sorting (MACS, Miltenyi). Approximately 1×10⁷ cells were induced from either the low or high mutation rate libraries, and both were first sorted for the expression of the V5 C-terminal tag, which indicated proper folding of the full-length protein. This was performed by incubating the cells with FITC-labeled anti-V5 antibody and selecting cells with anti-FITC microbeads for cell separation. After growth of the selected clones, cells were again induced to display RANKL protein, incubated with OPG-Fc, and washed, and those clones that did not bind to OPG were collected as the flow-through on a Protein A magnetic bead column. These cells were then labeled with RANK-Fc, and this time those clones that retained binding to the Protein A column were collected. After sorting, cells were allowed to multiply in selective medium, and this strategy was repeated twice to yield clones termed “LM3S” and “HM3S”. Approximately 200 individual colonies were isolated from the libraries and stained with OPG-Fc. Those clones with little to no detectable staining were then assessed for their ability to bind to RANK-Fc. DNA was extracted from the top scoring clones of interest with a yeast miniprep kit (Zymoprep) and used to transform chemically competent DH5α E. coli (Invitrogen) for sequencing. Individual point mutations were then added to the cDNA encoding RANKL by site-directed mutagenesis, and subsequent combinations were cloned in a similar fashion. A second round of error-prone PCR used the identical primers and protocol described earlier, but used as the starting template either of the F164Y/Q236H/F269Y or K194N/Q236H/F269Y triple mutants. Clones were selected over three rounds of sorting with three sequentially lower amounts of monomeric RANK-6×His and anti-6×His microbeads. Finally, the resulting library was incubated with RANK-6×His at room temperature for 10 min and then tested for the ability to outcompete the presence of unlabeled OPG at room temperature for 5 min. Residual RANK binding was detected with APC-labeled anti-6×His antibody. In the course of sorting, the K194E mutation was identified and used to replace the K194N mutation, which introduced a potential N-linked glycosylation site at the interface with RANK or OPG.

Assessment of Cell Viability with the MTT Assay

Cells were seeded in 96-well plates either in αMEM alone, WT htRANKL (200 ng/ml) alone or in combination with single-block, RANK^(high) (2,000 ng/ml), or only single-block, RANK^(high). After 3 days, a 1:10 dilution of MTT reagent (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide, Sigma-Aldrich) was added (final concentration of 0.5 mg/ml) to the culture medium and incubated at 37° C. After 3 hours, 150 μl of 0.04 N HCl in isopropanol was added to each well to stop the reaction, and MTT absorbance was determined at an OD of 595 nm.

Co-Culture Assays

Calvarial osteoblasts were isolated and expanded in number as previously described (37). Briefly, osteoblasts were isolated from the calvaria of three day-old pups by 3×20-min treatments with collagenase. Cells were expanded in number in α-MEM medium, and then were lifted and plated together with bone marrow-derived macrophages in a 96-well plate. Cells were co-cultured in the presence of 10 nM 1,25-Vitamin D3 in α-MEM medium with the indicated concentrations of single-block, RANK^(high) scRANKL. On day 7, cells were treated with 0.1% collagenase for 15 min to remove osteoblasts, and then were fixed for TRAP staining.

Intraperitoneal Injection of Mice with RANKL

Eight week-old female Balb/c mice were purchased from NCI Frederick, housed in the animal facility at Washington University School of Medicine, and maintained according to the guidelines set by the Association for Assessment and Accreditation of Laboratory Animal Care. All animal studies were approved by the Animal Studies Committee of Washington University School of Medicine. PBS, WT-SM RANKL (0.5 mg/kg), or WT-SM RANKL and single-block, RANK^(high) scRANKL (0.5 mg/kg) were injected intraperitoneally into the mice at 0, 24, and 48 hours, as previously described (38). Mice were sacrificed 1.5 hours after the third injection, and serum was collected by cardiac puncture. Serum concentrations of CTx were determined by ELISA according to the manufacturer's protocol (Immunodiagnostics Systems).

Example 10. Biological Sequences

The biological sequences for various TNFsf monomers, wild type scTNFsfL, scTNFsfL, peptide linkers, and DNA primers. National Center for Biotechnology Information (NCBI) database identifiers for certain sequences are also provided. These sequences, as well as related sequences of allelic variants, can be downloaded from the National Center for Biotechnology Information (NCBI) database on the world wide web at “ncbi.nlm.nih.gov/pubmed” using these identifiers and associated links.

TABLE 5 Biological sequences SEQ ID NO: Sequence Comments 1 MRRASRDYGKYLRSSEEMGSGPGVPHEGPLHPAPSAPA Mouse wt RANKL monomer PAPPPAASRSMFLALLGLGLGQVVCSIALFLYFRAQMD NCBI NM_011613.3 PNRISEDSTHCFYRILRLHENADLQDSTLESEDTLPDSCR RMKQAFQGAVQKELQHIVGPQRFSGAPAMMEGSWLD VAQRGKPEAQPFAHLTINAASIPSGSHKVTLSSWYHDR GWAKISNMTLSNGKLRVNQDGFYYLYANICFRHHETS GSVPTDYLQLMVYVVKTSIKIPSSHNLMKGGSTKNWS GNSEFHFYSINVGGFFKLRAGEEISIQVSNPSLLDPDQDA TYFGAFKVQDID 2 MRRASRDYTKYLRGSEEMGGGPGAPHEGPLHAPPPPA Human wt RANKL monomer PHQPPAASRSMFVALLGLGLGQVVCSVALFFYFRAQM NCBI AF019047.1 DPNRISEDGTHCIYRILRLHENADFQDTTLESQDTKLIPD SCRRIKQAFQGAVQKELQHIVGSQHIRAEKAMVDGSW LDLAKRSKLEAQPFAHLTINATDIPSGSHKVSLSSWYHD RGWAKISNMTFSNGKLIVNQDGFYYLYANICFRHHETS GDLATEYLQLMVYVTKTSIKIPSSHTLMKGGSTKYWSG NSEFHFYSINVGGFFKLRSGEEISIEVSNPSLLDPDQDAT YFGAFKVRDID 3 MSTESMIRDVELAEEALPQKMGGFQNSRRCLCLSLFSF Mouse wt TNF monomer LLVAGATTLFCLLNFGVIGPQRDEKFPNGLPLISSMAQT NCBI NM_013693.3 LTLRSSSQNSSDKPVAHVVANHQVEEQLEWLSQRANA LLANGMDLKDNQLVVPADGLYLVYSQVLFKGQGCPD YVLLTHTVSRFAISYQEKVNLLSAVKSPCPKDTPEGAEL KPWYEPIYLGGVFQLEKGDQLSAEVNLPKYLDFAESGQ VYFGVIAL 4 MSTESMIRDVELAEEALPKKTGGPQGSRRCLFLSLFSFL Human wt TNF monomer IVAGATTLFCLLHFGVIGPQREEFPRDLSLISPLAQAVRS NCBI NM_000594.3 SSRTPSDKPVAHVVANPQAEGQLQWLNRRANALLANG VELRDNQLVVPSEGLYLIYSQVLFKGQGCPSTHVLLTH TISRIAVSYQTKVNLLSAIKSPCQRETPEGAEAKPWYEPI YLGGVFQLEKGDRLSAEINRPDYLDFAESGQVYFGIIAL 5 MPSSGALKDLSFSQHFRMMVICIVLLQVLLQAVSVAVT Mouse wt TRAIL monomer YMYFTNEMKQLQDNYSKIGLACFSKTDEDFWDSTDGE NCBI NM_009425.2 ILNRPCLQVKRQLYQLIEEVTLRTFQDTISTVPEKQLSTP  PLPRGGRPQKVAAHITGITRRSNSALIPISKDGKTLGQKI  ESWESSRKGHSFLNHVLFRNGELVIEQEGLYYIYSQTYF  RFQEAEDASKMVSKDKVRTKQLVQYIYKYTSYPDPIVL  MKSARNSCWSRDAEYGLYSIYQGGLFELKKNDRIFVSV  TNEHLMDLDQEASFFGAFLIN  6 MAMMEVQGGPSLGQTCVLIVIFTVLLQSLCVAVTYVY Human wt TRAIL monomer FTNELKQMQDKYSKSGIACFLKEDDSYWDPNDEESMN NCBI NM_003810.3 SPCWQVKWQLRQLVRKMILRTSEETISTVQEKQQNISP  LVRERGPQRVAAHITGTRGRSNTLSSPNSKNEKALGRKI  NSWESSRSGHSFLSNLHLRNGELVIHEKGFYYIYSQTYF  RFQEEIKENTKNDKQMVQYIYKYTSYPDPILLMKSARN  SCWSKDAEYGLYSIYQGGIFELKENDRIFVSVTNEHLID  MDHEASFFGAFLVG  7 QPFAHLTINAASIPSGSHKVTLSSWYHDRGWAKISNMT Mouse WT Single Chain LSNGKLRVNQDGFYYLYANI S FRHHETSGSVPTDYLQL RANKL peptide MVYVVKTS E KIPSSHNLMKGGSTKNWSGNSEFHFYSIN sequence with solubility  VGGFFKLRAGEEISIQVSNPSLLDPDQDATYFGAFKVQD mutations (C220S/I246E)  ID   (mature; no signal peptide and GGSGGGSGGGSG no Hisx6 tag)  QPFAHLTINAASIPSGSHKVTLSSWYHDRGWAKISNMT  LSNGKLRVNQDGFYYLYANI S FRHHETSGSVPTDYLQL  MVYVVKTS E KIPSSHNLMKGGSTKNWSGNSEFHFYSIN  VGGFFKLRAGEEISIQVSNPSLLDPDQDATYFGAFKVQD  ID  GGSGGGSGGGSG  QPFAHLTINAASIPSGSHKVTLSSWYHDRGWAKISNMT  LSNGKLRVNQDGFYYLYANI S FRHHETSGSVPTDYLQL  MVYVVKTS E KIPSSHNLMKGGSTKNWSGNSEFHFYSIN  VGGFFKLRAGEEISIQVSNPSLLDPDQDATYFGAFKVQD  ID  SSGRENLYFQ  8 QPFAHLTINAASIPSGSHKVTLSSWYHDRGWAKISNMT Mouse Single Block, LSNGKLRVNQDGFYYLYANI S FRH N ETSGSVPTDYLQL RANKL^(High) peptide MVYVVKTS E KIPSSHNLMKGGSTKNWSGNSEFHFYSIN sequence with solubility  VGGFFKLRAGEEISIQVSNPSLLDPDQDATYFGAFKVQD mutations (C220S/I246E)  ID   (mature; no signal peptide and GGSGGGSGGGSG no Hisx6 tag)  QPFAHLTIN R ASIPSGSHKVTLSSWYHDR A WAKISNMT Set 1 mutations in Table 4.  LSNGKLRVNQDGFYYLYANI S FRHHETSGSVPTDYLQL Linker length predicted to  MVYVVKTS E KIPSSHNLMKGGSTKNWSGNSEFHFYSIN restrict folding to Left-hand  VGGFFKLRAGEEISIQVSNPSLLDPDQDATYFGAFKVQD only.  ID  GGSGGGSGGGSG  QPFAHLTIN R ASIPSGSHKVTLSSWYHDR A WAKISNMT  LSNGKLRVNQDGFYYLYANI S FRHHETSGSVPTDYLQL  MVYVVKTS E K R PSSHNLMKGGSTKNWSGNSEFHFYSI  NVGGFFKLRAGEEISIQVSNPSLLDPDQDATYFGAFKVQ  DID  SSGRENLYFQ  9 QPFAHLTIN R ASIPSGSHKVTLSSWYHDR A WAKISNMT Mouse Double Block, LSNGKLRVNQDGFYYLYANI S FRHHETSGSVPTDYLQL RANKL^(High) peptide MVYVVKTS E KI R SSHNLMKGGSTKNWSGNSEFHFYSI sequence with solubility NVGGFFKLRAGEEISIQVSNPSLLDPDQDATYFGAFKVQ mutations (C220S/I246E) DID (mature; no signal peptide and GGSGGGSGGGSG no Hisx6 tag) QPFAHLTINAASIPSGSHKVTLSSWYHDRGWAKISNMT Set 1 mutations in Table 4. LSNGKLRVNQDGFYYLYANI S FRHNETSGSVPTDYLQL Linker length predicted to MVYVVKTS E K R PSSHNLMKGGSTKNWSGNSEFHFYSI restrict folding to Left-hand NVGGFFKLRAGEEISIQVSNPSLLDPDQDATYFGAFKVQ only. DID  SSGRENLYFQ 10 QPFAHLTINAASIPSGSHKVTLSSWYHDRGWAKISNMT Mouse Single Block, LSNGKLRVNQDGFYYLYANI S FR GGS HHETSGSVPTDY RANKL^(High) peptide L H LMVYVVKTS E KIPSSHNLMKGGSTKNWSGNSEFHF sequence with solubility YSINVGGFFKLRAGEEISIQVSNPSLLDPDQDATYFGAF mutations (C220S/I246E) KVQDID (mature; no signal peptide and GGSGGGSGGGSG no Hisx6 tag) QPFAHLTINAASIPSGSHKVTLSSWYHDRGWA E ISNMT Set 2 mutations in Table 4. LSNGKLRVNQDGFYYLYANI S FRHHETSGSVPTDYL H L  MVYVVKTS E KIPSSHNLMKGGSTKNWSGNSE YY FYSI  NVGGFFKLRAGEEISIQVSNPSLLDPDQDATYFGAFKVQ  DID  GGSGGGSGGGSG  QPFAHLTINAASIPSGSHKVTLSSWYHDRGWA E ISNMT  LSNGKLRVNQDGFYYLYANI S FRHHETSGSVPTDYL H L  MVYVVKTS E KIPSSHNLMKGGSTKNWSGNSE YY FYSI  NVGGFFKLRAGEEISIQVSNPSLLDPDQDATYFGAFKVQ  DID  SSGRENLYFQ  11 QPFAHLTINAASIPSGSHKVTLSSWYHDRGWAKISNMT Mouse Double Block, LSNGKLRVNQDGFYYLYANI S FR GGS HHETSGSVPTDY RANKL^(High) peptide L H LMVYVVKTS E KIPSSHNLMKGGSTKNWSGNSEFHF sequence with solubility YSINVGGFFKLRAGEEISIQVSNPSLLDPDQDATYFGAF mutations (C220S/I246E) KVQDID (mature; no signal peptide and GGSGGGSGGGSG no Hisx6 tag) QPFAHLTINAASIPSGSHKVTLSSWYHDRGWAKISNMT Set 2 mutations in Table 4. LSNGKLRVNQDGFYYLYANI S FR GGS HHETSGSVPTDY L H LMVYVVKTS E KIPSSHNLMKGGSTKNWSGNSEFHF YSINVGGFFKLRAGEEISIQVSNPSLLDPDQDATYFGAF  KVQDID  GGSGGGSGGGSG  QPFAHLTINAASIPSGSHKVTLSSWYHDRGWA E ISNMT  LSNGKLRVNQDGFYYLYANI S FRHHETSGSVPTDYL H L  MVYVVKTS E KIPSSHNLMKGGSTKNWSGNSE YY FYSI  NVGGFFKLRAGEEISIQVSNPSLLDPDQDATYFGAFKVQ  DID  SSGRENLYFQ  12 AQPFAHLTINATDIPSGSHKVSLSSWYHDRGWAKISNM Human WT Single Chain TFSNGKLIVNQDGFYYLYANI S FRHHETSGDLATEYLQ RANKL peptide sequence with LMVYVTKTS E KIPSSHTLMKGGSTKYWSGNSEFHFYSI solubility mutations NVGGFFKLRSGEEISIEVSNPSLLDPDQDATYFGAFKVR (C221S/I247E) (mature; no DID signal peptide) GGSGGGSGGGSG AQPFAHLTINATDIPSGSHKVSLSSWYHDRGWAKISNM TFSNGKLIVNQDGFYYLYANI S FRHHETSGDLATEYLQ LMVYVTKTS E KIPSSHTLMKGGSTKYWSGNSEFHFYSI NVGGFFKLRSGEEISIEVSNPSLLDPDQDATYFGAFKVR DID GGSGGGSGGGSG AQPFAHLTINATDIPSGSHKVSLSSWYHDRGWAKISNM TFSNGKLIVNQDGFYYLYANI S FRHHETSGDLATEYLQ LMVYVTKTS E KIPSSHTLMKGGSTKYWSGNSEFHFYSI NVGGFFKLRSGEEISIEVSNPSLLDPDQDATYFGAFKVR DID 13 AQPFAHLTINATDIPSGSHKVSLSSWYHDRGWAKISNM Human Single Block, TFSNGKLIVNQDGFYYLYANI S FRH N ETSGDLATEYLQ RANKL^(High) peptide LMVYVTKTS E KIPSSHTLMKGGSTKYWSGNSEFHFYSI sequence with solubility NVGGFFKLRSGEEISIEVSNPSLLDPDQDATYFGAFKVR mutations (C221S/I247E) DID (mature; no signal peptide) GGSGGGSGGGSG Set 6 mutations in Table 4. AQPFAHLTIN R TDIPSGSHKVSLSSWYHDR A WAKISNM Linker length predicted to TFSNGKLIVNQDGFYYLYANI S FRHHETSGDLATEYLQ restrict folding to Left-hand LMVYVTKTS E KIPSSHTLMKGGSTKYWSGNSEFHFYSI only. NVGGFFKLRSGEEISIEVSNPSLLDPDQDATYFGAFKVR DID GGSGGGSGGGSG AQPFAHLTIN R TDIPSGSHKVSLSSWYHDR A WAKISNM TFSNGKLIVNQDGFYYLYANI S FRHHETSGDLATEYLQ LMVYVTKTS E K R PSSHTLMKGGSTKYWSGNSEFHFYSI NVGGFFKLRSGEEISIEVSNPSLLDPDQDATYFGAFKVR DID 14 AQPFAHLTINATDIPSGSHKVSLSSWYHDRGWAKISNM Human Double Block, TFSNGKLIVNQDGFYYLYANI S FRH N ETSGDLATEYLQ RANKL^(High) peptide LMVYVTKTS E K R PSSHTLMKGGSTKYWSGNSEFHFYSI sequence with solubility NVGGFFKLRSGEEISIEVSNPSLLDPDQDATYFGAFKVR mutations (C221S/I247E) DID (mature; no signal peptide) GGSGGGSGGGSG Set 6 mutations in Table 4. AQPFAHLTIN R TDIPSGSHKVSLSSWYHDRGWAKISNM Linker length predicted to TFSNGKLIVNQDGFYYLYANI S FRH N ETSGDLATEYLQ restrict folding to Left-hand LMVYVTKTS E KIPSSHTLMKGGSTKYWSGNSEFFIFYSI only. NVGGFFKLRSGEEISIEVSNPSLLDPDQDATYFGAFKVR DID GGSGGGSGGGSG AQPFAHLTIN R TDIPSGSHKVSLSSWYHDR A WAKISNM TFSNGKLIVNQDGFYYLYANI S FRHHETSGDLATEYLQ LMVYVTKTS E K R PSSHTLMKGGSTKYWSGNSEFHFYSI NVGGFFKLRSGEEISIEVSNPSLLDPD QDATYFGAFKVRDID 15 AQPFAHLTINATDIPSGSHKVSLSSWYHDRGWAKISNM Human Single Block, TFSNGKLIVNQDGFYYLYANI S FR GGS HHETSGDLATE RANKL^(High) peptide YL H LMVYVTKTS E KIPSSHTLMKGGSTKYWSGNSEFH sequence with solubility FYSINVGGFFKLRSGEEISIEVSNPSLLDPDQDATYFGAF mutations (C221S/I247E) KVRDID (mature; no signal peptide) GGSGGGSGGGSG Set 7 mutations in Table 4. AQPFAHLTINATDIPSGSHKVSLSSWYHDRGWA E ISNM TFSNGKLIVNQDGFYYLYANI S FRHHETSGDLATEYL H LMVYVTKTS E KIPSSHTLMKGGSTKYWSGNSE YY FYSI NVGGFFKLRSGEEISIEVSNPSLLDPDQDATYFGAFKVR DID GGSGGGSGGGSG AQPFAHLTINATDIPSGSHKVSLSSWYHDRGWA E ISNM TFSNGKLIVNQDGFYYLYANI S FRHHETSGDLATEYLQ LMVYVTKTS E KIPSSHTLMKGGSTKYWSGNSE YY FYSI NVGGFFKLRSGEEISIEVSNPSLLDP 16 AQPFAHLTINATDIPSGSHKVSLSSWYHDRGWAKISNM Human Double Block, TFSNGKLIVNQDGFYYLYANI S FR GGS HHETSGDLATE RANKL^(High) peptide YL H LMVYVTKTS E KIPSSHTLMKGGSTKYWSGNSEFH sequence with solubility FYSINVGGFFKLRSGEEISIEVSNPSLLDPDQDATYFGAF mutations (C221S/I247E) KVRDID (mature; no signal peptide) GGSGGGSGGGSG Set 7 mutations in Table 4. AQPFAHLTINATDIPSGSHKVSLSSWYHDRGWAKISNM TFSNGKLIVNQDGFYYLYANI S FR GGS HHETSGDLATE YL H LMVYVTKTS E KIPSSHTLMKGGSTKYWSGNSEFH FYSINVGGFFKLRSGEEISIEVSNPSLLDPDQDATYFGAF KVRDID GGSGGGSGGGSG AQPFAHLTINATDIPSGSHKVSLSSWYHDRGWA E ISNM TFSNGKLIVNQDGFYYLYANI S FRHHETSGDLATEYL H LMVYVTKTS E KIPSSHTLMKGGSTKYWSGNSE YY FYSI NVGGFFKLRSGEEISIEVSNPSLLDPDQDATYFGAFKVR DID 17 SDKPVAHVVANPQAEGQLQWLNRRANALLANGVELR Human WT Single Chain TNF DNQLVVPSEGLYLIYSQVLFKGQGCPSTHVLLTHTISRI peptide sequence AVSYQTKVNLLSAIKSPCQRETPEGAEAKPWYEPIYLG (mature; no signal peptide). GVFQLEKGDRLSAEINRPDYLDFAESGQVYFGIIAL GGSGGGSGGGSG SDKPVAHVVANPQAEGQLQWLNRRANALLANGVELR DNQLVVPSEGLYLIYSQVLFKGQGCPSTHVLLTHTISRI AVSYQTKVNLLSAIKSPCQRETPEGAEAKPWYEPIYLG GVFQLEKGDRLSAEINRPDYLDFAESGQVYFGIIAL GGSGGGSGGGSG SDKPVAHVVANPQAEGQLQWLNRRANALLANGVELR DNQLVVPSEGLYLIYSQVLFKGQGCPSTHVLLTHTISRI AVSYQTKVNLLSAIKSPCQRETPEGAEAKPWYEPIYLG GVFQLEKGDRLSAEINRPDYLDFAESGQVYFGIIAL 18 SDKPVAHVVANPQAEGQLQWLNRRANALLANGVELR Human Single Block, TNF^(High) DNQLVVPSEGLYLIYSQVLFKGQGCPSTHVLLTHTISRI peptide sequence (mature; no AVS Q QTKVNLLSAIKSPCQRETPEGAEAKPWYEPIYLG signal peptide) GVFQLEKGDRLSAEINRPDYLDFAESGQVYFGIIAL Set 16 mutations in Table 4. GGSGGGSGGGSG SDKPVAHVVANPQAEGQLQWLNRRANALLANGVELR DNQLVVPSEGLYLIYSQVLFKGQGCPSTHVLLTHTISRI AV T YQTKVNLLSAIKSPCQRETPEGAEAKPWYEPIYLG GVFQLEKGDRLSAEINRPDYLDFAESGQVYFGIIAL GGSGGGSGGGSG SDKPVAHVVANPQAEGQLQWLNRRANALLANGVELR DNQLVVPSEGLYLIYSQVLFKGQGCPSTHVLLTHTISRI AV T YQTKVNLLSAIKSPCQRETPEGAEAKPWYEPIYLG GVFQLEKGDRLSAEINRPDYLDFAESGQVYFGIIAL 19 SDKPVAHVVANPQAEGQLQWLNRRANALLANGVELR Human Double Block, TNF^(High) DNQLVVPSEGLYLIYSQVLFKGQGCPSTHVLLTHTISRI peptide sequence (mature; no AVS Q QTKVNLLSAIKSPCQRETPEGAEAKPWYEPIYLG signal peptide) GVFQLEKGDRLSAEINRPDYLDFAESGQVYFGIIAL Set 16 mutations in Table 4. GGSGGGSGGGSG SDKPVAHVVANPQAEGQLQWLNRRANALLANGVELR DNQLVVPSEGLYLIYSQVLFKGQGCPSTHVLLTHTISRI AVS Q QTKVNLLSAIKSPCQRETPEGAEAKPWYEPIYLG GVFQLEKGDRLSAEINRPDYLDFAESGQVYFGIIAL GGSGGGSGGGSG SDKPVAHVVANPQAEGQLQW T NR F ANALLANGVELR DNQLVVPSEGLYLIYSQVLFKGQGCPSTHVLLTHTISRI AV T YQTKVNLLSAIKSPCQRETPEGAEAKPWYEPIYLG GVFQLEKGDRLSAEINRPDYLDFAESGQVYFGIIAL 20 SDKPVAHVVANPQAEGQLQWLNRRANALLANGVELR Human Single Block, TNF^(High) DNQLVVPSEGLYLIYSQVLFKGQGCPSTHVLLTHTISRI peptide sequence (mature; no AVSYQTKVNLLSAIKSPCQRETPEGAEAKPWYEPIYLG signal peptide) GVFQLEKGDRLSAEINRPDYL V FAESGQVYFGIIAL Set 17 mutations in Table 4. GGSGGGSGGGSG SDKPVAHVVANPQAEGQLQW T NRFANALLANGVELR DNQLVVPSEGLYLIYSQVLFKGQGCPSTHVLLTHTISRI AVSYQTKVNLLSAIKSPCQRETPEGAEAKPWYEPIYLG GVFQLEKGDRLSAEINRPDYLDFAESGQVYFGIIAL GGSGGGSGGGSG SDKPVAHVVANPQAEGQLQW T NR F ANALLANGVELR DNQLVVPSEGLYLIYSQVLFKGQGCPSTHVLLTHTISRI AVSYQTKVNLLSAIKSPCQRETPEGAEAKPWYEPIYLG GVFQLEKGDRLSAEINRPDYLDFAESGQVYFGIIAL 21 SDKPVAHVVANPQAEGQLQWLNRRANALLANGVELR Human Double Block, TNF^(High) DNQLVVPSEGLYLIYSQVLFKGQGCPSTHVLLTHTISRI peptide sequence (mature; no AVSYQTKVNLLSAIKSPCQRETPEGAEAKPWYEPIYLG signal peptide) GVFQLEKGDRLSAEINRPDYL V FAESGQVYFGIIAL Set 17 mutations in Table 4. GGSGGGSGGGSG SDKPVAHVVANPQAEGQLQWLNRRANALLANGVELR DNQLVVPSEGLYLIYSQVLFKGQGCPSTHVLLTHTISRI AVSYQTKVNLLSAIKSPCQRETPEGAEAKPWYEPIYLG GVFQLEKGDRLSAEINRPDYL V FAESGQVYFGIIAL GGSGGGSGGGSG DKPVAHVVANPQAEGQLQW T NR F ANALLANGVELRD NQLVVPSEGLYLIYSQVLFKGQGCPSTHVLLTHTISRIA VSYQTKVNLLSAIKSPCQRETPEGAEAKPWYEPIYLGG VFQLEKGDRLSAEINRPDYLDFAESGQVYFGIIAL 22 PQRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWESS Human WT Single Chain RSGHSFLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEI TRAIL peptide sequence KENTKNDKQMVQYIYKYTSYPDPILLMKSARNSCWSK (mature; no signal peptide). DAEYGLYSIYQGGIFELKENDRIFVSVTNEHLIDMDHEA SFFGAFLVG GGSGGGSGGGSG PQRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWESS RSGHSFLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEI KENTKNDKQMVQYIYKYTSYPDPILLMKSARNSCWSK DAEYGLYSIYQGGIFELKENDRIFVSVTNEHLIDMDHEA SFFGAFLVG GGSGGGSGGGSG PQRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWESS RSGHSFLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEI KENTKNDKQMVQYIYKYTSYPDPILLMKSARNSCWSK DAEYGLYSIYQGGIFELKENDRIFVSVTNEHLIDMDHEA SFFGAFLVG 23 PQRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWESS Human Single Block, TRAIL^(High) RSGHSFLSNLHLRNGELVIHEKGFYYIYSQT A FRF S EEIK peptide sequence (mature; no ENTKNDKQMVQYIYKYTSYPDPILLMKSARNSCWSKD signal peptide) AEYGLYSIYQGGIFELKENDRIFVSVTNEHLIDMDHEAS Set 23 mutations in Table 4. FFGAFLVG Linker length predicted to GGSGGGSGGGSG restrict folding to Left-hand PQRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWESS only. RSGHSFLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEI KENTKNDKQMVQYIYKYTSYPDPILLMKSARNSCWSK DAEYGLYSIYQGGIFELKENDRIFVSVTNEHLIDM H HEA SFFGAFLVG GGSGGGSGGGSG PQRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWESS RSGHSFLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEI KE V T R NDKQMVQYIYK W T D YPDPILLMKSARNSCWS KDAEYGLYSIYQGGIFELKENDRIFVSVTNEHLIDM H HE ASFFGAFLVG 24 PQRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWESS Human Double Block, RSGHSFLSNLHLRNGELVIHEKGFYYIYSQT A FRF S EEIK TRAIL^(High) ENTKNDKQMVQYIYKYTSYPDPILLMKSARNSCWSKD peptide sequence (mature; no AEYGLYSIYQGGIFELKENDRIFVSVTNEHLIDMDHEAS signal peptide) FFGAFLVG Set 23 mutations in Table 4. GGSGGGSGGGSG Linker length predicted to PQRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWESS restrict folding to Left-hand RSGHSFLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEI only. KE V T R NDKQMVQYIYK W T D YPDPILLMKSARNSCWS KDAEYGLYSIYQGGIFELKENDRIFVSVTNEHLIDM H HE ASFFGAFLVG GGSGGGSGGGSG PQRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWESS RSGHSFLSNLHLRNGELVIHEKGFYYIYSQT A FRF S EEIK E V T R NDKQMVQYIYK W T D YPDPILLMKSARNSCWSK DAEYGLYSIYQGGIFELKENDRIFVSVTNEHLIDMDHEA SFFGAFLVG 25 MGILPSPGMPALLSLVSLLSVLLMGCVA signal peptide from pHLsec 26 SSGRENLYFQGHHHHHH tobacco etch virus (TEV) protease cleavage site and a 6x-histidine tag 27 SSGRENLYFQ TEV cleavage product of SEQ ID NO: 27 28 ATGTGGGTGTTCAAGTTTCTGC Cathepsin K primer (forward) 29 CCACAAGATTCTGGGGACTC Cathepsin K primer (reverse) 30 CCCGTCACATTCTGGTCCAT NFATc1 primer (forward) 31 CAAGTAACCGTGTAGCTGCACAA NFATc1 primer (reverse) 32 CAGCTCCCTAGAAGATGGATTCAT TRAP primer (forward) 33 GTCAGGAGTGGGAGCCATATG TRAP primer (reverse) 34 TTCGACTACGGCCAGATGATT β3 primer (forward) 35 GGAGAAAGACAGGTCCATCAAGT β3 primer (reverse) 36 AGCATACAGGTCCTGGCATC Cyclophilin primer (forward) 37 TTCACCTTCCCAAAGACCAC Cyclophilin primer (reverse) 38 GGSG Peptide linker 39 GGGS Peptide linker 40 GGGGS Peptide linker 41 GSAT Peptide linker 42 PQRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWESS Human Single Block, TRAIL^(High) RSGHSFLSNLHLRNGELVIHEKGFYYIYSQT N F K F R EEI peptide sequence (mature; no KE R T H NDKQMVQYIYKYT D YPDPILLMKSARNSCWSK signal peptide) DAEYGLYSIYQGGIFELKENDRIFVSVTNE R L LQ MDHE Set 24 mutations in Table 4. ASFFGAFLVG Linker length predicted to GGSGGGSGGGSG restrict folding to Left-hand PQRVAAHITGTR R RSNTLSSPNSKNEKALGRKINSWESS only. R R GHSFLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEI KE R T H NDKQMVQYIYKYT D YPDPILLMKSARNSCWSK DAEYGLYSIYQGGIFELKENDRIFVSVTNEHLIDMDHEA SFFGAFLVG GGSGGGSGGGSG PQRVAAHITGTR R RSNTLSSPNSKNEKALGRKINSWESS R R GHSFLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEI KENTKNDKQMVQYIYKYTSYPDPILLMKSARNSCWSK DAEYGLYSIYQGGIFELKENDRIFVSVTNEHLIDMDHEA SFFGAFLVG 43 QRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWESS  Human Double Block, RSGHSFLSNLHLRNGELVIHEKGFYYIYSQT N F K F R EEI TRAIL^(High) KE R T H NDKQMVQYIYKYT D YPDPILLMKSARNSCWSK peptide sequence (mature; no DAEYGLYSIYQGGIFELKENDRIFVSVTNE R L LQ MDHE signal peptide) ASFFGAFLVG Set 24 mutations in Table 4. GGSGGGSGGGSG Linker length predicted to QRVAAHITGTR R RSNTLSSPNSKNEKALGRKINSWESS restrict folding to Left-hand R R GHSFLSNLHLRNGELVIHEKGFYYIYSQTYFRFQEEI only. KENTKNDKQMVQYIYKYTSYPDPILLMKSARNSCWSK DAEYGLYSIYQGGIFELKENDRIFVSVTNEHLIDMDHEA SFFGAFLVG GGSGGGSGGGSG QRVAAHITGTRGRSNTLSSPNSKNEKALGRKINSWESS RSGHSFLSNLHLRNGELVIHEKGFYYIYSQT N F K F R EEI KENTKNDKQMVQYIYKYTSYPDPILLMKSARNSCWSK DAEYGLYSIYQGGIFELKENDRIFVSVTE R L LQ MDHEA SFFGAFLVG 44 FRGGSHHET Sequence generated by an insertion of GGS after R222 in strand C of RANKL

In certain scTNFsfL presented in Table 5, the monomers and peptide linkers are shown on separate lines. In certain instances, portions of a TEV cleavage site are shown on a separate line. Mutations in certain TNFsf monomers are shown in boldface and are underlined.

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The breadth and scope of the present disclosure should not be limited by any of the above-described embodiments in the Examples, but should be defined only in accordance with the following claims and their equivalents. 

1. A recombinant single chain polypeptide comprising a first TNF superfamily (TNFsf) monomer, a second TNFsf monomer, and a third TNFsf monomer operably linked with peptide linkers, wherein the recombinant single chain polypeptide forms a trimer; the trimer comprises: (i) a first receptor binding site comprising a first gain of function variant (increases binding avidity to a target TNFsfR); (ii) a second receptor binding site comprising a second gain of function variant (increases binding avidity to a target TNFsfR); and (iii) a third receptor binding site comprising a loss of function variant (decreases binding avidity or blocks binding to target receptor); and the trimer has a high avidity for a target TNFsf receptor (e.g., RANK) and a low avidity to non-target TNFsf receptors (e.g., OPG).
 2. A method of enhancing binding avidity to a target TNFsfR while suppressing the binding avidity to a non-target TNFsfR comprising administering to a subject in need thereof a therapeutically effective amount of the recombinant single chain polypeptide of claim
 1. 3. The recombinant single chain polypeptide of claim 1 or the method of claim 2, wherein the receptor binding site (or interface/cleft) is comprised of apposed monomers forming the receptor-binding sites, wherein the shape of the binding clefts determine receptor selectivity.
 4. The recombinant single chain polypeptide of claim 1 or the method of claim 2, wherein the TNFsf is selected from RANKL, TNFα, TRAIL, or APRIL, or a functional fragment thereof.
 5. The recombinant single chain polypeptide of claim 1 or the method of claim 2, wherein the first monomer, second monomer, and third monomer comprises: at least 85% sequence identity to residues 165 to 314 of SEQ ID NO: 2 and the trimer has RANK binding activity.
 6. The recombinant single chain polypeptide of claim 1 or the method of claim 2, wherein the first monomer, second monomer, and third monomer comprises at least 85% sequence identity to residues 86 to 233 of SEQ ID NO: 4 or a functional fragment thereof and the trimer has TNFR1 binding activity.
 7. The recombinant single chain polypeptide of claim 1 or the method of claim 2, wherein the first monomer, second monomer, and third monomer comprises at least 85% sequence identity to residues 120 to 280 of SEQ ID NO: 6 or a functional fragment thereof and the trimer has DR5 binding activity.
 8. The recombinant single chain polypeptide of claim 1 or the method of claim 2, wherein the first monomer, second monomer, and third monomer comprises at least 85% sequence identity to residues 115 to 250 of SEQ ID NO:45 or a functional fragment thereof and the trimer has TACI binding activity.
 9. The recombinant single chain polypeptide or method of claim 4, wherein the TNFsf member is RANKL, the target TNFsf receptor is RANK and the non-target TNFsf receptor is OPG.
 10. The recombinant single chain polypeptide or method of claim 4, wherein the TNFsf member is TNF, the target TNFsf receptor is TNFR1 and the non-target TNFsf receptor is TNFR2.
 11. The recombinant single chain polypeptide or method of claim 4, wherein the TNFsf member is TRAIL, the target TNFsf receptor is DR5 and the non-target TNFsf receptor is DR4.
 12. The recombinant single chain polypeptide or method of claim 4, wherein the TNFsf member is APRIL, the target TNFsf receptor is TACI and the non-target Tumor Necrosis Factor superfamily receptor is BCMA.
 13. The recombinant single chain polypeptide or method of claim 5, wherein (i) the first receptor binding site comprising a first gain of function variant increasing binding avidity to a target RANK; and (ii) the second receptor binding site comprising a second gain of function variant increasing binding avidity to a target RANK; wherein the first or second gain of function variant is selected from the group consisting of A172R, K195E, Q237H, Q237T, H271Y, F270Y, and combinations thereof.
 14. The recombinant single chain polypeptide or method of claim 13, wherein (iii) the third receptor binding site comprising a loss of function variant decreasing binding avidity or blocking binding to non-target OPG; wherein the loss of function variant is selected from the group consisting of a substitution of AA″ loop residues 177-185 (SGSHKVSLS) for SSS; GGS after R223 in strand C, yielding FR-GGS-HHET; G192A, K195E, F270Y, H271Y, Q237H, Q237T; H225N, H271Y, I249R, R223A, R223Q, R223Y, and combinations thereof.
 15. The recombinant single chain polypeptide or method of claim 13, wherein the first, second, or third receptor binding site comprises a solubility mutation selected from the group consisting of I247Q, I247E, I247K, I247R, C221S, and combinations thereof.
 16. The recombinant single chain polypeptide or method of claim 6, wherein (i) the first receptor binding site comprising a first gain of function variant increasing binding avidity to a target TNFR1; and (ii) the second receptor binding site comprising a second gain of function variant increasing binding avidity to a target TNFR1; wherein the first or second gain of function variant is selected from the group consisting of L105T, R108F, A160T, V161S, V161T, S162A, S162V, S162T, Q164S, Q164P, T165H, T165G, E222T, and combinations thereof.
 17. The recombinant single chain polypeptide or method of claim 16, wherein (iii) the third receptor binding site comprising a loss of function variant decreasing binding avidity or blocking binding to non-target TNFR2; wherein the loss of function variant is selected from the group consisting of L105T, R108F, A160T, V161T, S162A, S162T, Q164S, T165G, S175Y, L151R, E222T; or N110Q, L151R, Y163Q, Y163G, Y163L, Y163K, Y163T, S175Y, D219V; and combinations thereof.
 18. The recombinant single chain polypeptide or method of claim 7, wherein (i) the first receptor binding site comprising a first gain of function variant increasing binding avidity to a target DR5; and (ii) the second receptor binding site comprising a second gain of function variant increasing binding avidity to a target DR5; wherein the first or second gain of function variant is selected from the group consisting of G131R, R1491, S159R, N199R, K201H, S215D, D269H, and combinations thereof.
 19. The recombinant single chain polypeptide or method of claim 18, wherein (iii) the third receptor binding site comprising a loss of function variant decreasing binding avidity or blocking binding to non-target DR4; wherein the loss of function variant is selected from the group consisting of D269H, Y189N, R191K, Q193R, H264R, I266L, D267Q; Y189A, Y189N, R191K, Q193R, Q193S, N199V, K201R, Y213W, S215D, H264R, I266L, D267Q; and combinations thereof.
 20. The recombinant single chain polypeptide or method of claim 8, wherein (i) the first receptor binding site comprising a first gain of function variant increasing binding avidity to a target TACI; and (ii) the second receptor binding site comprising a second gain of function variant increasing binding avidity to a target TACI; wherein the first or second gain of function variant is R206M.
 21. The recombinant single chain polypeptide or method of claim 20, wherein (iii) the third receptor binding site comprising a loss of function variant decreasing binding avidity or blocking binding to non-target TACI; wherein the loss of function variant is selected from the group consisting of R206E, R206M, and combinations thereof.
 22. A recombinant nucleic acid, encoding the recombinant single chain polypeptide of claim 1, wherein the recombinant nucleic acid is operably linked to a promoter or a nucleic acid encoding a signal peptide, wherein the signal peptide provides for secretion of the recombinant single chain polypeptide when expressed in a host cell.
 23. An isolated host cell containing the recombinant nucleic acid of claim
 22. 24. A method for producing a recombinant single chain polypeptide, comprising the steps of: (i) growing the isolated host cell of claim 22; and (ii) harvesting an encoded single chain polypeptide from the isolated host cell that comprises the recombinant nucleic acid and expresses the recombinant single chain polypeptide or from media in which the isolated host cell was grown, wherein the recombinant single chain polypeptide forms a trimer having a high avidity for a target TNFsf receptor (e.g., RANK) and a low avidity to non-target TNF receptors (e.g., OPG).
 25. A composition comprising the recombinant single chain polypeptide of claim 1 and a pharmaceutically acceptable excipient. 